Lactic acid synergized non-thermal processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage

Abstract

The present invention provides a processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage, comprising: mixing a vegetable with a brine, performing fermentation and then performing the following steps: A) mixing the remainder of a fermentation broth for the fermented vegetables with water and lactic acid to obtain a pretreated packaging fermentation broth; B) treating the pretreated packaging fermentation broth by using a plasma jet device to obtain a treated packaging fermentation broth; and C) mixing the fermented vegetables with the treated packaging fermentation broth, and then packaging the mixture. 20 25 20 03 18 16 J an 2 02 5 A B S T R A C T 2 0 2 5 2 0 0 3 1 8 1 6 J a n 2 0 2 5 A B S T R A C T 2 0 2 5 2 0 0 3 1 8 1 6 J a n 2 0 2 5 7 / 7 FIG. 7 7 / 7 a 20000 Comparative Example 5 Example 5 b.o 16000 Example 6 12000 8000 0 1 3 5 7 Storage duration (days) b Comparative Example 5 1600 Example 5 Example 6 1200 800 400 0 1 3 5 7 Storage duration (days) FIG. 7 20 25 20 03 18 16 J an 2 02 5 7 / 7 1 6 J a n 2 0 2 5 1 6 0 0 0 2 0 2 5 2 0 0 3 1 8 I 8 0 0 0 0 3 5 7 b 1 6 0 0 + 1 2 0 0 C h e w i n e s s 8 0 0 4 0 0 0 3 5 7 F I G . 7 7 / 7 1 6 J a n 2 0 2 5 1 6 0 0 0 2 0 2 5 2 0 0 3 1 8 I 8 0 0 0 0 3 5 7 b 1 6 0 0 + 1 2 0 0 C h e w i n e s s 8 0 0 4 0 0 0 3 5 7 F I G . 7

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of Chinese Patent Application No. 2024113457502, filed on September 25, 2024, and the disclosure of which is hereby incorporated by reference. TECHNICAL FIELD

[0002] The present invention relates to the technical field of biological fermentation, and in particular, to a lactic acid synergized non-thermal processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage. BACKGROUND OF THE INVENTION

[0003] As one of traditional fermented foods in China, fermented vegetables can be traced back to the Shang Dynasty 3000 years ago, and are passed down to this day. As consumers pursuit flavor and mouthfeel of fermented vegetables and have improved food safety and health awareness, low-salt fermented vegetables (non-sterilized) have become the development trend of the industry. Low-salt fermented vegetables are prepared through closed anaerobic fermentation of fresh vegetables rich in cellulose with low-concentration brine (with the content of salt below 4%). In a process of “cold processing” (fermentation), lactic acid bacteria attached to the surfaces of vegetables metabolize vegetable nutrients to produce acid and aroma, thereby generating a variety of flavor substances and taste substances and giving fermented vegetables a unique sour and fragrant flavor.

[0004] Because the activity of lactic acid bacteria, unique fermentation aroma and crisp mouthfeel of the low-salt fermented vegetables are sensitive to heat, they are usually transported and sold directly through a cold chain instead of being thermally sterilized in actual production. However, during the period of logistics and shelf storage, because the products are still being fermented, many microorganisms can degrade macromolecular substances such as cellulose, 2025200318   16 Jan 2025 pectin and protein by producing a variety of plant cell wall degrading enzymes, leading to the textural deterioration and inferior mouthfeel of non-sterilized low-salt fermented vegetables, which seriously affects the quality of the products. The paper “Post-acidification of stored low-salt pickles and influence of post-acidification on the quality and safety of the pickles” disclosed that the post-acidification of the low-salt fermented vegetables during storage had adverse effects on their texture, flavor and color. At present, existing related patent documents (for example, application numbers: 201910610951.3, 202310914220.4) and some papers reported that main methods for protecting crispness of pickled vegetables are chemical methods, such as addition of exogenous additives that are not naturally produced by fermentation or contained in raw materials of food. Such exogenous additives include calcium chloride, calcium lactate, immobilized pectin methylesterase, calcium ascorbate sustained release capsules, and the like. Although these food additives can maintain the crispness of the pickled vegetables to a certain extent, they all affect the original flavor or appearance of pickles to varying degrees, and are contrary to the current trend of using the additives as little as possible in food industry. In addition, most of fermented vegetables that maintain their crispness with the additives are mainly pickled vegetables, and will be packaged in vacuum and then pasteurized. They are quite different from the non-sterilized low-salt fermented vegetables of the present invention. Therefore, without the additional provision of the crispness-maintaining additives and complicated processing procedures, the study and use of a non-thermal processing method for alleviating the textural deterioration of instant pickles during storage are of great significance.

[0005] Therefore, it is highly necessary to develop a method for improving the texture of packaged fermented vegetables during storage. SUMMARY OF THE INVENTION

[0006] In view of this, the technical problem to be solved by the present invention is to provide a lactic acid synergized non-thermal processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage, by which the textural deterioration of the fermented vegetables during transportation and storage can be effectively alleviated. The treated low-salt fermented vegetables have good quality and crisp mouthfeel.

[0007] Plasma-activated water (PAW) technology is a new processing technology with low 2025200318   16 Jan 2025 destructiveness, by which water is treated to be non-thermal plasma. The PAW contains active nitrogen-oxygen radicals, oxidants and charged high-energy particles, and has many advantages, such as low energy consumption, good sterilization effect, little damage to the sensory quality of thermo-sensitive food and no secondary pollution. PAW is easy to prepare, safe in application, efficient in production and low in cost. It has been found from existing studies that DBD (dielectric barrier discharge) treatment based on plasma generated in the air can improve the texture of fermented vegetables to some extent, but this method can be carried out only in special packaging boxes without fermentation broth and with a certain amount of air. Its application has been limited when used in low-salt fermented vegetables that have been subjected to viable bacteria fermentation and industrial production. For PAW, most studies have shown that it can reduce pathogenic microorganisms on the surface of fresh-cut vegetables and fresh meat after being treated.

[0008] The inventor creatively found that the synergetic treatment of lactic acid (an organic acid) and PAW can solve the problem and improve the texture of the packaged fermented vegetables during storage. According to the present invention, the PAW and lactic acid synergized non-thermal processing method is applied to the packaged low-salt fermented vegetables, which can effectively slow down the growth of pectinase-producing microorganisms in a fermentation system, slow down the decline of pectins in vegetables during storage, and inhibit the textural deterioration of pickles during storage. Such a method is simple in process and convenient in operation.

[0009] The present invention provides a processing method for controlling textural deterioration of low-salt fermented vegetables during storage. The method takes the advantages of the synergetic effect of lactic acid treatment and PAW non-thermal treatment. In the method of the present invention, the fresh vegetables are mixed with a brine and a fermentation is performed, and then the following steps are performed:

[0010] A) taking out the vegetables after fermentation, mixing the remainder of the fermentation broth with water and a lactic acid solution to obtain a pretreated packaging fermentation broth;

[0011] B) treating the pretreated packaging fermentation broth by using a plasma jet device to obtain a treated packaging fermentation broth; and 2025200318   16 Jan 2025

[0012] C) mixing the fermented vegetables with the treated packaging fermentation broth to generate a mixture, and then packaging the mixture.

[0013] As used herein, the term “remainder of the fermentation broth” refers to the remaining liquid after taking out the fermented vegetables from the fermentation system containing vegetables and broth when fermentation is completed.

[0014] According to the method of the present invention, preparation of vegetable raw materials for fermentation is performed first by: washing the vegetable raw materials for fermentation with running water for 5 min-20 min to remove impurities such as surface sediment, cutting the vegetable raw materials into pieces with appropriate sizes, and then fermenting the vegetables.

[0015] The fresh cleaned and cut vegetables are mixed with a brine according to the ratio of vegetables to brine=1:2 (w / v) and the mixture is placed in an earthen jar for natural fermentation or fermentation by inoculating lactic acid bacteria. The opening of the jar is sealed by water. After fermentation, fermented vegetables have a certain total acidity and a number of lactic acid bacteria.

[0016] The term “total acidity of the fermented vegetables” refers to the acidity in the fermented vegetables, which is counted by the concentration of lactic acid and measured by regular acid-base neutralization titration method. The term “natural fermentation” refers to a fermentation carried out by utilizing microorganisms naturally present in the air and vegetables without adding additional microorganisms.

[0017] According to the present invention, the brine is prepared by:

[0018] weighing Illicium verum, Zanthoxylum bungeanum, Rhizoma Kaempferiae, dried capsicum, glucose and salt; adding purified water to fully dissolve the weighed substances to obtain a mixed solution; heating and boiling the mixed solution; cooling the mixed solution to ambient temperature; and filtering the mixed solution with a filter cloth to prepare the brine.

[0019] In a preferred embodiment of the present invention, the mass ratio of Illicium verum, Zanthoxylum bungeanum, Rhizoma Kaempferiae, dried capsicum, glucose and salt is 0.8: 0.6: 0.7: 0.7: 2: 3.5-4; and the heating time is 40min-50min, and specifically 40min, 45min and 50min, or a value between the ranges of any two of the above. The ambient temperature is 2025200318   16 Jan 2025 15°C-30°C; and the mesh number of the filter cloth is200 to 500.

[0020] The fermentation temperature of the present invention is 25°C-30°C, and specifically 25°C, 27°C, 30°C, or a value between the ranges of any two of the above. The fermentation time is 2d-7d, and specifically 2d, 3d, 4d, 5d, 6d or 7d, or a value between the ranges of any two of the above.

[0021] The fermentation is determined to be completed under the following conditions: the total acidity of the fermented vegetables being 0.3%-0.5%, the total number of lactic acid bacteria being 106 -109 CFU / ml, and the salinity of the fermented vegetables being less than 4.0%.

[0022] The mass ratio of the vegetables and the brine is 1: 2; and the vegetable cleaning time is 5min-20min. Specifically, the vegetable cleaning time is 5min, 10min, 20min, or a value between the ranges of any two of the above.

[0023] The remainder of a fermentation broth for the fermented vegetables after fermentation, which is an untreated fermentation broth, is mixed with water and lactic acid solution to obtain a pretreated packaging fermentation broth. The term “packaging fermentation broth” used herein refers to the liquid for packaging with the fermented vegetables in a packaging bag.

[0024] The pretreatment of the packaging fermentation broth includes the follow steps: after the completion of the fermentation of the vegetables and brine, taking out the fermented vegetables from the earthen jar, mixing the remainder of fermentation broth (the remainder of the fermentation broth for the fermented vegetables) with sterile drinking water and lactic acid to obtain the pretreated packaging fermentation broth.

[0025] The concentration of the lactic acid solution used in the present invention is 1%-2%, and specifically 1%, 1.5%, 2%, or a value between any two of the above. The total acidity of the obtained pretreated packaging fermentation broth is 0.6%-1%, and specifically 0.6%, 0.8%, 1.0%, or a value between any two of the above. The salinity is 2.5%-4%.

[0026] The pretreated packaging fermentation broth is treated by using a plasma jet device to obtain the treated packaging fermentation broth.

[0027] According to the present invention, parameters of the treatment by the plasma jet device include: 2025200318   16 Jan 2025

[0028] the muzzle of the plasma jet device being placed 10mm below a liquid level and under conditions of an ambient temperature of 20°C-25°C, a flow rate of an air carrier gas of 15L / min-25L / min, a working current of 0.024mA, a working voltage of 19kV, a frequency of 20kHz, and a treatment time of 80s-180s.

[0029] In a preferred embodiment of the present invention, the parameters of the treatment by the plasma jet device include:

[0030] the muzzle of the plasma jet device being placed 10mm below a liquid level and under conditions of an ambient temperature of 20°C-25°C, a flow rate of an air carrier gas of 15L / min-25L / min, a working current of 0.024mA, a working voltage of 19kV, a frequency of 20kHz, and a treatment time of 80s-160s.

[0031] The fermented vegetables are mixed with the treated packaging fermentation broth. The mass ratio of the fermented vegetables and the treated packaging fermentation broth is 1:1.

[0032] According to the present invention, the vegetables include but are not limited to green vegetables, white radishes or red radishes.

[0033] According to the present invention, the packaging may be air packaging, vacuum packaging or nitrogen packaging. The vacuum packaging of the present invention is preferably that a sample bag is sealed in vacuum to 0.2 atmospheric pressure by using a vacuum packaging machine.

[0034] The method of the present invention can obviously alleviate deterioration of texture properties such as the hardness and chewiness of the packaged low-salt pickles during the subsequent storage for 5-10 days, so that the products can maintain a fresh crisp mouthfeel for a long time, and the sour and fragrant sensory quality of the low-salt fermented vegetables can be effectively maintained. The method avoids the influence of additives added in a conventional process on the products, and makes the product more nutritious and healthy. Moreover, this method can reduce the content of pectinase-producing microorganisms, can significantly prolong the shelf life of the packaged low-salt fermented vegetables, and meet the requirements of large-scale automatic production of the fermented vegetables with local characteristics.

[0035] According to the present invention, a lactic acid synergized physical non-thermal processing method is used to alleviate the textural deterioration of the packaged fermented 2025200318   16 Jan 2025 vegetables during storage. In this method, lactic acid which is an organic acid commonly presented in the fermented vegetables is added and works with PAW for synergetic treatment and then together packaged with the low-salt fermented vegetables, so that the influence of additives added in a conventional process on products is avoided, chemical residues are not generated in a cold sterilization process, and enzymes causing the textural deterioration are effectively inhibited. As a result, the stability of storage quality is improved, and the obtained products are more nutritious and healthy. In addition, such a treatment method is simple and can satisfy the requirements for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0036] FIG. 1 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage.

[0037] FIG. 2 shows the growth of pectinase-producing microorganisms in screening media in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage.

[0038] FIG. 3 shows changes of pectins in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage.

[0039] FIG. 4 shows changes of hardness and chewiness of untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage.

[0040] FIG. 5 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in untreated low-salt vegetable mustards (control group) and treated low-salt fermented vegetable mustards (treatment group) during the 7-day storage.

[0041] FIG. 6 shows changes of pectins in untreated low-salt fermented vegetable mustards (control group) and treated low-salt fermented vegetable mustards (treatment group) during the 7-day storage.

[0042] FIG. 7 shows changes of hardness and chewiness of untreated low-salt fermented 2025200318   16 Jan 2025 vegetable mustards (control group) and treated low-salt fermented vegetable mustards (treatment group) during the 7-day storage. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention provides a lactic acid synergized non-thermal processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage, and persons skilled in the art can learn from the contents of the present invention and appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are apparent to the persons skilled in the art, and all fall within the scope of protection of the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application herein without departing from the content, spirit and scope of the present invention, so as to realize and apply the technology of the present invention.

[0044] It should be understood that the expression “one or more of......” individually includes each of the objects described after the expression and various combinations of two or more of the described objects, unless otherwise understood from the context. The expression “and / or” in combination with three or more described objects should be understood to have the same meaning unless otherwise understood from the context.

[0045] Terms “including”, “having” or “containing”, including the use of grammatical synonyms, should generally be understood as being open and non-restrictive, such as not excluding other elements or steps not described, unless otherwise specifically stated or otherwise understood from the context.

[0046] In this application, the term “and / or” describes the relationship of related objects and means that there can be three kinds of relationships, for example, A and / or B, which can mean that A exists alone, both A and B exist, and B exists alone. A and B can be singular or plural.

[0047] It should be understood that the sequence of steps or the sequence in which certain actions are performed is not important as long as the present invention is still operable. In addition, two or more steps or actions can be carried out simultaneously.

[0048] The use of any and all examples or exemplary language such as “for example” or 2025200318   16 Jan 2025 “including” herein is intended only to better illustrate the present invention and does not limit the scope of the present invention unless claims are put forward. No language in the description should be interpreted as indicating that any unclaimed element is essential to the practice of the present invention.

[0049] In addition, the numerical range and parameters used to define the present invention are approximate values, and the relevant numerical values in embodiments have been presented as accurately as possible here. However, any numerical value inevitably contains standard deviation caused by individual test methods. Therefore, unless explicitly stated otherwise, it should be understood that all ranges, quantities, values and percentages used in the disclosure are qualified by the word “about”. Here, “about” usually means that the actual value is within plus or minus 10%, 5%, 1% or 0.5% of a specific value or range.

[0050] It should be understood that in various embodiments of the present application, the sequence number of the above-mentioned processes does not mean the execution sequence, and some or all steps can be executed concurrently or sequentially, and the execution sequence of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of this application.

[0051] Some cases are recorded in the examples and comparative examples of the present invention, in which the examples show some implementations of the present invention. However, this does not mean that the effects of the present invention can be achieved only in these cases.

[0052] In order to further illustrate the present invention, a lactic acid synergized non-thermal processing method for controlling textural deterioration of packaged low-salt fermented vegetables during storage, provided by the present invention, is detailed with reference to the embodiments. Example 1

[0053] The example provides a lactic acid synergizd non-thermal processing method for controlling textural deterioration of packaged low-salt fermented radishes during storage, and the method includes the following steps:

[0054] (1) Preparation for raw materials: clean white radishes with running water for 5 min to 2025200318   16 Jan 2025 remove impurities such as surface sediments, and cut them into the ones with appropriate sizes.

[0055] (2) Making of brine: weigh 0.8% (m / v) Illicium verum, 0.6% (m / v) Zanthoxylum bungeanum, 0.7% (m / v) Rhizoma Kaempferiae, 0.7% (m / v) dried capsicum, 2% (m / v) glucose and 3.5% (m / v) salt; add purified water to fully dissolve them to obtain a mixed solution; heat and boil the mixed solution for 45min; cool the mixed solution to an ambient temperature (15°C-30°C); and filter the mixed solution with a 300-mesh filter cloth to obtain the brine.

[0056] (3) Low-salt fermentation: mix cleaned and cut radishes with the brine at the ratio of vegetables and brine=1:2 (w / v), place the mixture into an earthen jar, control the fermentation temperature of the mixture at 25C±2C, perform fermentation for 4 days until the total acidity of the radishes being 0.4%, the total number of lactic acid bacteria being 107 CFU / ml, and the salinity of the fermented radishes being 2.5% are satisfied, and end up the fermentation.

[0057] (4) Preparation of pretreated packaging fermentation broth: adjust the total acidity of fermented broth to 0.7% and the salinity thereof to 2.5% with sterile drinking water and a lactic acid solution with a concentration of 1.0%.

[0058] (5) Place a PAW jet device (Suzhou Yirun, Cat. PAW-1) in the pretreated packaging fermentation broth (20-50L) prepared in (4), and place the muzzle thereof 10mm below the liquid level; then, set a flow rate of an air carrier gas of 15L / min-25L / min, a working voltage of 19kV, a frequency of 20kHz, a current of 0.024mA, and a treatment time of 80s at the ambient temperature of 20°C-25°C, to obtain the treated packaging fermentation broth.

[0059] (6) Packaging: add back the fermented radishes in (3) into the treated packaging fermentation broth in (5) at the ratio of 1:1 (w / v), and then place the mixture in a packaging bag for being directly sealed (air packaging). Example 2

[0060] Example 2 is the same as Example 1, except that the PAW treatment time in Step (5) is 160s. 2025200318   16 Jan 2025 Example 3

[0061] Example 3 is the same as Example 1, except that: in Step (3), cleaned and cut radishes are mixed with the brine at the ratio of vegetables and brine=1:2 (w / v), the mixture is placed into an earthen jar, a solution containing lactic acid bacteria (leuconostoc mesenteroides accounting for 4% of the total weight of materials are used, with the content of viable bacteria not less than 109CFU / mL) is added, the fermentation temperature of the mixture is controlled at 25°C±2°C, the mixture is fermented for 2 days until the total acidity of pickles being 0.4%, the total number of lactic acid bacteria being 108 CFU / ml, and the salinity of the fermented radishes being 2.5% are satisfied, and the fermentation is ended up. Example 4

[0062] Example 4 is the same as Example 1, except that in Step (6), the fermented radishes and the treated packaging fermentation broth are placed in a packaging bag at the ratio of 1:1 (w / v), and the bag is sealed in vacuum to 0.2 atmospheric pressure by using a vacuum packaging machine. Comparative Example 1

[0063] Comparative Example 1 is the same as Example 1, except that the packaging fermentation broth in Steps (4) and (5) is not treated. Comparative Example 2

[0064] Comparative Example 2 is the same as Example 1, except that treatment in Step (4) is not carried out, and since 1.0% lactic acid is not used in Step (4) to adjust the acidity of the packaging fermentation broth, it is necessary to perform fermentation for a longer time in Step (3), until the acidity in the fermentation system reaches 0.7%, and the subsequent steps are carried out after the fermentation. 2025200318   16 Jan 2025 Comparative Example 3

[0065] Comparative Example 3 is the same as Example 1, except that, in Step (5), PAW is not used to treat the pretreated packaging fermentation broth. Comparative Example 4

[0066] (1) Preparation for raw materials: clean white radishes with running water for 5 min to remove impurities such as surface sediments, and cut them into the ones with appropriate sizes.

[0067] (2) Making of brine: weigh 0.8% (m / v) Illicium verum, 0.6% (m / v) Zanthoxylum bungeanum, 0.7% (m / v) Rhizoma Kaempferiae, 0.7% (m / v) dried capsicum, 2% (m / v) glucose and 3.5% (m / v) salt; add purified water to fully dissolve them to obtain a mixed solution; heat and boil the mixed solution for 45min; cool the mixed solution to an ambient temperature (15°C-30°C); and filter the dissolving solution with a 300-mesh filter cloth to prepare the brine.

[0068] (3) Low-salt fermentation: mix cleaned and cut radishes with the brine at the ratio of vegetables and brine=1:2 (w / v), place the mixture into an earthen jar, control the fermentation temperature of the mixture at 25C±2C, perform fermentation for 7 days until the total acidity of the white radishes being 0.7%, the total number of lactic acid bacteria being 107 CFU / ml, and the salinity of the fermented radishes being 2.5% are satisfied, and end up the fermentation.

[0069] (4) Preparation of pretreated packaging fermentation broth: adjust the total acidity of fermented broth to 0.7% and the salinity thereof to 2.5% with sterile drinking water.

[0070] (5) Add the fermented radishes in Step (3) and the packaging fermentation broth in Step (4) at the ratio of 1:1 (w / v) in a polypropylene food container (150mmx100mmx30mm) smaller than the upper and lower electrode plates of DBD, then seal and package the container with a polyethylene film, and treat it for 60s at the DBD voltage of 70kV and the frequency of 50Hz for four times.

[0071] (6) Packaging: place the treated sample in Step (5) in a packaging bag and seal it directly (air packaging).

[0072] Packaged fermented radishes obtained in Examples 1, 2, 3 and 4 and Comparative Examples 1, 2, 3 and 4 are stored for 7 days at 30C, and then their texture properties are 2025200318   16 Jan 2025 determined to evaluate their quality at the 7th day. The results are shown in Table 1. Comparison of Examples 1, 2, 3 and 4 in Table 1 with Comparative Example 1 shows that the hardness and chewiness of the treated low-salt fermented radishes are respectively increased by 32.6%, 57.7%, 24.3% and 67.2%, 44.2%, 67.1%, 51.1% and 71.8% in the same environment. Moreover, the hardness and chewiness of the treated fermented radishes in Examples 1, 2, 3 are more effectively maintained by adjusting the fermentation mode or packaging mode than those in Comparative Example 1, which indicates that the lactic acid and PAW synergized non-thermal processing method can alleviate the textural deterioration of packaged fermented vegetables. Comparative Example 2 and Comparative Example 4 show the effects of separate treatment of PAW and DBD on the texture of the fermented radishes, respectively. When Comparative Example 2 and Comparative Example 4 are compared with Comparative Example 1, the results of hardness and chewiness show that single treatment has a certain effect, but the improvement level is lower than that of the synergy treatment of PAW and lactic acid. Especially in Comparative Example 4, a regular packaging box needs to be used when the fermented radishes are treated and then the fermented radishes are transferred to the packaging bag. However, the packaging bag being placed directly on the electrode plate will puncture the packaging bag because of uneven media on the electrode plate, and the treatment process is more complicated.

[0073] Table 1 Comparison of texture properties of Examples 1, 2, 3 and 4 and Comparative Examples 1, 2 and 3 of the present invention Hardness (g) Chewiness Example 1 11176±237 434±17 Example 2 13288±218 503±8 Example 3 10477±311 455±21 Example 4 14092±1281 517±12 Comparative Example 1 8426±401 301±27 Comparative Example 2 8926±371 347±2 Comparative Example 3 7960±462 260±29 Comparative Example 4 9005±135 342±12 2025200318   16 Jan 2025

[0074] In order to further clarify the change of the storage process, the fermented white radish samples in Examples 1, 2 and Comparative Example 1 are stored for 7 days at 30°C, and the hardness and chewiness of radishes are determined by a texture analyzer (TAXTPlus, Stable Micro System) at the 0, 1st, 3rd, 5th and 7th day respectively. The unit of hardness is g (the size of 1g of the quality of the material to which the heavy force is applied) and chewiness is the energy required to chew a solid sample into a stable state for swallowing, expressed in units of force or without units. The total number of lactic acid bacteria in the fermented radishes is determined according to Chinese National Standard GB4789.35-2016, the number of Escherichia coli in the fermented radishes is determined according to Chinese National Standard GB 4789.3-2016, a pectin substrate screening plate is used to determine the total number of pectinase-producing microorganisms, and carbazole colorimetry method is used to determine the content of pectin.

[0075] The changes of the total number of lactic acid bacteria, the number of Escherichia coli and the total number of pectinase-producing microorganisms in the low-salt fermented radishes in Examples 1, 2 and Comparative Example 1 during storage are shown in FIG. 1 and Table 2. FIG. 1 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage, where FIG. 1a shows the total number of lactic acid bacteria, FIG. 1b shows the number of Escherichia coli, and FIG. 1c shows the number of pectinase-producing bacteria. Table 2 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in fermented radishes in control group and treatment group during the 7-day storage. It can be seen from figures and tables that the low-salt fermented radishes in the comparative examples and the examples have no obvious difference in the content of lactic acid bacteria with probiotic properties during the 7-day storage, and no pathogenic bacteria such as Escherichia coli have been detected, which indicates that the obtained products are safe and healthy. 2025200318   16 Jan 2025 Table 2 The total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in fermented radishes (control group) and treated fermented radish (treatment group) during 7-day storage The number of microorganisms Fermentation days Comparative Example 1 Example 1 Example 2 0 7.24±0.02 7.11±0.01 7.23±0.01 1 7.83±0.01 7.65±0.04 7.69±0.02 Lactic acid bacteria 3 8.50±0.01 8.86±0.02 8.56±0.00 5 8.82±0.02 8.47±0.00 8.61±0.02 7 8.42±0.01 8.56±0.01 8.59±0.02 0 ND ND ND 1 ND ND ND Escherichia coli 3 ND ND ND 5 ND ND ND 7 ND ND ND 0 1.55±0.02 ND ND Pectinase-producing 1 3.42±0.01 2.51±0.01 2.31±0.05 3 3.52±0.02 2.70±0.01 2.48±0.01 microorganism 5 5.38±0.01 3.63±0.02 2.37±0.01 7 5.54±0.03 3.56±0.01 2.75±0.10 Note: ND means no detection

[0076] The growth plates of pectinase-producing microorganisms in the untreated low-salt fermented radishes (control group) and the low-salt fermented radishes treated with lactic acid synergized PAW (treatment group) in Example 1 and Comparative Example 1 after 7-day storage are shown in FIG. 2 and Table 3. FIG. 2 shows the growth of pectinase-producing microorganisms in the screening media in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage. It can be seen from FIG. 2 and FIG. 1c that the growth of pectinase-producing microorganisms in fermented radishes non-thermally treated by lactic acid synergized PAW is significantly lower than that in fermented radishes (control group) during storage, which indicates that the treatment method of 2025200318   16 Jan 2025 the present invention has a very significant effect on slowing down the growth of pectinase-producing microorganisms.

[0077] The changes of pectins in low-salt fermented radishes in Examples 1, 2 and Comparative Example 1 during storage are shown in FIG. 3. FIG. 3 shows the changes of pectins in untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage. Table 3 shows the changes of pectins in fermented radishes in control group and treatment group during the 7-day storage. It can be seen from the figure that the pectins of the fermented radishes in Examples 1, 2 is significantly higher than that in Comparative Example 1 in different storage periods, and the decrease rate of the pectin during storage in Examples 1, 2 is lower than that in Comparative Example 1. Table 3 Changes of pectins in untreated fermented radishes (control group) and treated fermented radishes (treatment group) during the 7-day storage Pectin / pmol / mL Fermentation days Comparative Example 1 Example 2 Example 1 0 1.45±0.03 1.44±0.03 1.43±0.03 1 1.30±0.02 1.37±0.04 1.40±0.08 3 1.11±0.10 1.35±0.03 1.39±0.01 5 0.83±0.06 1.22±0.05 1.32±0.04 7 0.71±0.03 1.12±0.01 1.29±0.03

[0078] The changes of hardness and chewiness of low-salt fermented radishes in Examples 1, 2 and Comparative Example 1 during storage are shown in FIG. 4 and Table 4. FIG. 4 shows the changes of hardness and chewiness of untreated low-salt fermented radishes (control group) and treated low-salt fermented radishes (treatment group) during the 7-day storage, where FIG. 4a shows hardness and FIG. 4b shows chewiness. Table 4 shows the changes of texture properties of fermented radishes in the control group and the treatment group during the 7-day storage. It can be seen from the figure that the hardness and chewiness of treated fermented vegetables in the present invention are significantly higher than those in the comparative example during the entire storage. 2025200318   16 Jan 2025 Table 4 Changes of texture properties of fermented radishes in control group and treatment group during the 7-day storage Texture Fermentation Comparative Example 1 Example 2 properties days Example 1 0 21577±542 20982±1286 22500±123 1 15896±1330 16764±1367 17178±1461 Hardness / g 3 10161±823 13124±344 13920±560 5 8826±371 12171±462 13821±123 7 8426±401 11176±237 13288±218 0 1118±9 1088±33 1107±32 1 842±29 1012±45 1023±21 Chewiness 3 751±14 821±22 883±3 5 533±27 552±25 604±21 7 301±1 433±18 503±8 Example 5 non-thermal processing method for alleviating textural deterioration of packaged low-salt fermented mustard greens

[0079] (1) Preparation for raw materials: clean the wide-stem mustards for fermentation with running water for 10 min to remove impurities such as surface sediments, and cut them into the ones with appropriate sizes.

[0080] (2) Making of brine: weigh 0.8% (m / v) Illicium verum, 0.6% (m / v) Zanthoxylum bungeanum, 0.7% (m / v) Rhizoma Kaempferiae, 0.7% (m / v) dried capsicum, 6% (m / v) salt and 2% (m / v) glucose; add purified water to fully dissolve them to obtain a mixed solution; heat and boil the mixed solution for 45min; cool the mixed solution to an ambient temperature (15°C-30°C); and filter the dissolving solution with a 300-mesh filter cloth to prepare the brine.

[0081] (3) Low-salt fermentation: mix cleaned and cut green vegetables with the brine at the ratio of vegetables and brine=1:2 (w / v), place the mixture into an earthen jar, control the fermentation temperature of the mixture at 30C, perform fermentation for 7 days until the total acidity of the mustard greens being 0.5%, the total number of lactic acid bacteria being 106 2025200318   16 Jan 2025 CFU / ml, and the salinity of the fermented mustard greens being 4.0% are satisfied, and end up the fermentation.

[0082] (4) Preparation of pretreated packaging fermentation broth: adjust the total acidity of fermented broth to 1.0% and the salinity thereof to 4.0% with sterile drinking water and lactic acid solution with a concentration of 2.0%.

[0083] (5) Place a PAW jet device in the pretreated packaging fermentation broth in Step (4), and place the muzzle thereof 10mm below the liquid level; then, set a flow rate of an air carrier gas of 15L / min-25L / min, a working voltage of 19kV, a frequency of 20kHz, a current of 0.024mA, and a treatment time of 100s at the ambient temperature of 20C-25C, to obtain the treated packaging fermentation broth.

[0084] (6) Packaging: add the fermented mustard greens in (3) into the treated packaging fermentation broth in (5) at the ratio of 1:1 (w / v), and then place the mixture in a packaging bag for being directly sealed (air packaging). Example 6

[0085] Example 6 is the same as Example 5, except that the PAW treatment time in Step (5) is 180s. Comparative Example 5

[0086] Comparative Example 5 is the same as Example 5, except that the packaging fermentation broth in Steps (4) and (5) is not treated.

[0087] In order to further clarify the change of the storage process, the fermented mustard samples in Examples 5, 6 and Comparative Example 4 are stored for 7 days at 30°C in an accelerating manner, and the hardness and chewiness of fermented mustard greens are determined by a texture analyzer at the 0, 1st, 3rd, 5th and 7th day respectively. The total number of lactic acid bacteria in the fermented mustard greens is determined according to GB4789.35-2016, the number of Escherichia coli in the fermented mustard greens is determined according to GB 4789.3-2016, a pectin substrate screening plate is used to determine the total 2025200318   16 Jan 2025 number of pectinase-producing microorganisms, and carbazole colorimetry is used to determine the pectin.

[0088] The changes of the total number of lactic acid bacteria, the number of Escherichia coli and the total number of pectinase-producing microorganisms in the low-salt fermented mustard greens in Examples 5, 6 and Comparative Example 5 during storage are shown in FIG. 5 and Table 5. FIG. 5 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in untreated low-salt fermented mustard greens (control group) and treated low-salt fermented mustard greens (treatment group) during the 7-day storage, where FIG. 5a shows the change of the total number of lactic acid bacteria, FIG. 5b shows the testing results of Escherichia coli, and FIG. 5c shows the growth of pectinase-producing bacteria. Table 5 shows the total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in fermented mustard greens in control group and treatment group during 7-day storage.

[0089] A conclusion similar to that of fermented radishes can be drawn from the figures, that is, there is little difference in the number of beneficial lactic acid bacteria in the comparative examples and examples, and no Escherichia coli is detected. This ensures the safety of non-thermally sterilized products. In addition, the change of pectinase-producing microorganisms also shows that the treatment method of the present invention has a very significant effect on slowing down the growth of pectinase-producing microorganisms. Table 5 The total number of lactic acid bacteria, the number of Escherichia coli and the growth of pectinase-producing microorganisms in untreated fermented mustard greens (control group) and treated fermented mustard greens (treatment group) during 7-day storage The number of microorganisms Fermentation days Comparative Example 5 Example 5 Example 6 0 5.95±0.23 5.65±0.12 5.57±0.33 1 6.83±0.01 6.65±0.04 6.69±0.02 Lactic acid bacteria 3 7.26±0.13 6.96±0.12 7.27±0.17 5 8.05±0.05 7.90±0.22 7.87±0.08 7 7.42±0.01 7.62±0.07 7.72±0.16 2025200318   16 Jan 2025 0 ND ND ND 1 ND ND ND Escherichia coli 3 ND ND ND 5 ND ND ND 7 ND ND ND 0 2.37±0.16 ND ND Pectinase-producing 1 3.62±0.24 1.81±0.10 1.31±0.05 3 4.52±0.01 2.66±0.10 2.12±0.09 microorganism 5 5.47±0.05 3.63±0.11 2.80±0.04 7 6.00±0.11 4.06±0.16 2.99±0.09

[0090] The changes of pectins in low-salt fermented mustard greens in Examples 5, 6 and Comparative Example 5 during storage are shown in FIG. 6 and Table 6. FIG. 6 shows changes of pectins in untreated low-salt fermented mustard greens (control group) and treated low-salt fermented mustard greens (treatment group) during the 7-day storage. Protopectin is a polygalacturonic acid condensate containing methoxy group, and is bonded to cellulose and hemicellulose to adhere cells and maintain tissue hardness. Table 6 shows changes of pectins in fermented mustard greens in control group and treatment group during the 7-day storage. It can be seen from FIG. 6 that the fermented mustard greens in Examples 5, 6 contain more pectins than the fermented mustard greens in Comparative Example 5 in different periods during storage, and the pectins decrease more slowly during storage. Table 6 Changes of pectins in the fermented mustard greens in control group and treatment group during the 7-day storage Fermentation days Pectin / pmol / mL Comparative Example 5 Example 5 Example 6 0 3.55±0.01 3.76±0.03 3.78±0.01 1 2.99±0.02 3.34±0.04 3.65±0.03 3 2.66±0.05 3.37±0.03 3.33±0.01 5 1.79±0.06 2.75±0.02 2.97±0.02 7 1.65±0.02 2.72±0.01 3.01±0.03 2025200318   16 Jan 2025

[0091] The changes of hardness and chewiness of low-salt fermented mustard greens in Examples 5, 6 and Comparative Example 5 during storage are shown in FIG. 7 and Table 6. FIG. 7 shows the changes of hardness and chewiness of untreated low-salt fermented mustard greens (control group) and treated low-salt fermented mustard greens (treatment group) during the 7-day storage, where FIG. 7a shows the change of the hardness and FIG. 7b shows the change of the chewiness. Table 6 shows the changes of texture properties of fermented mustard greens in control group and treatment group during the 7-day storage. It can be seen from the figures that the hardness and chewiness of treated fermented mustard greens in the present invention are significantly higher than those in the comparative example during the entire storage. With the increase of storage duration, the hardness and chewiness of the comparative example become worse. However, in the example, the deterioration rates of texture-related indexes of the low-salt fermented mustard greens during storage are significantly slow down during storage. Table 6 Changes of texture properties of fermented radishes in control group and treatment group during the 7-day storage Texture properties Fermentation days Comparative Example 5 Example 5 Example 6 0 15361±442 15679±286 16157±323 1 10100±530 14902±367 14369±461 Hardness / g 3 9593±223 12557±144 14130±260 5 7345±171 11096±262 12836±173 7 6877±101 8235±237 9968±188 0 1575±12 1532±23 1565±42 1 982±9 1083±35 1309±21 Chewiness 3 856±24 893±12 1077±13 5 599±17 627±21 730±18 7 421±10 533±12 644±20

[0092] To sum up, according to the present invention, the PAW and lactic acid synergized non-thermal processing method is applied to the low-salt fermented vegetables, which can effectively slow down the growth of pectinase-producing microorganisms in the fermentation system, slow down the decline of pectins in vegetables during storage, and inhibit the textural 2025200318   16 Jan 2025 deterioration of fermented vegetables during storage. The method is simple in process and convenient in operation.

[0093] The above is only the preferred embodiment of the present invention, and it should be noted that persons skilled in the art can make several improvements and embellishments without departing from the principle of the present invention, and these improvements and embellishments should also be regarded as the protection scope of the present invention.

Claims

1. A processing method for low-salt fermented vegetables, comprisingmixing a vegetable with a brine, performing fermentation and then performing the following steps:A) mixing the remainder of a fermentation broth for the fermented vegetables with water and a lactic acid solution to obtain a pretreated packaging fermentation broth;B) treating the pretreated packaging fermentation broth by using a plasma jet device to obtain a treated packaging fermentation broth; andC) mixing the fermented vegetables with the treated packaging fermentation broth to generate a mixture, and then packaging the mixture.

2. The processing method according to claim 1, wherein the concentration of the lactic acid solution in Step A) is 1%-2%, the acidity of the pretreated packaging fermentation broth is 0.6%-1%, and the salinity of the pretreated packaging fermentation broth is 2.5%-4%.

3. The processing method according to claim 1, wherein parameters of the plasma jet device in Step B) are:the muzzle of the plasma jet device being placed 10mm below a liquid level and under conditions of an ambient temperature of 20°C-25°C, a flow rate of an air carrier gas of 15L / min-25L / min, a working current of 0.024mA, a working voltage of 19kV, a frequency of 20kHz, and a treatment time of 80s-180s.

4. The processing method according to claim 1, wherein the fermented vegetables in Step C) is prepared by:cleaning and cutting vegetables, mixing the cut vegetables with the brine, performing a natural fermentation or a fermentation by inoculating lactic acid bacteria to obtain the fermented vegetables.

5. The processing method according to claim 4, wherein the brine is prepared by:weighing Illicium verum, Zanthoxylum bungeanum, Rhizoma Kaempferiae, dried capsicum, glucose and salt; adding purified water to fully dissolve the weighed substances to obtain a2025200318   16 Jan 2025mixed solution; heating and boiling the mixed solution; cooling the mixed solution to an ambient temperature; and filtering the mixed solution with a filter to obtain the brine; whereinthe mass ratio of Illicium verum, Zanthoxylum bungeanum, Rhizoma Kaempferiae, dried capsicum, glucose and salt is 0.8: 0.6: 0.7: 0.7: 2: 3.5-4; the heating time is 40min-50min; the ambient temperature is 15°C-30°C.

6. The processing method according to claim 4, wherein the fermentation temperature is 25°C-30°C, the fermentation time is 2-7 days, and the fermentation is completed under the following conditions: the total acidity of the fermented vegetables being 0.3%-0.5%, the total number of the lactic acid bacteria being 106 CFU / ml-109 CFU / ml, and the salinity of the fermented vegetables being less than 4.0%.

7. The processing method according to claim 1, wherein the mass ratio of the vegetables and the brine is 1: 2.

8. The processing method according to claim 1, wherein the mass ratio of the fermented vegetables to the treated packaging fermentation broth is 1:1.

9. The processing method according to claim 1, wherein the packaging in Step C) is air packaging, vacuum packaging or nitrogen packaging.

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