A pickled vegetable and a method for preparing the same

Abstract

The present application belongs to the field of food processing, and provides a pickled vegetable and a preparation method thereof; a pickled vegetable mother liquor containing oligosaccharides and mint extract is prepared, a composite microbial inoculum composed of lactic acid bacteria and Weissella is inoculated into the pickled vegetable mother liquor, and the inoculated pickled vegetable mother liquor is injected into pretreated fresh vegetables for fermentation. In the fermentation process, first, the facultative anaerobic lactic acid bacteria consume the oxygen in the fermentation jar, and the oligosaccharides proliferate the Weissella, and the generated carbon dioxide speeds up the formation of an anaerobic environment. In this process, the yeast can still move, and the bacteriostatic substance produced by the movement of the lactobacillus has a weak inhibitory effect. Therefore, the addition of the mint extract improves the bacteriostatic effect of the yeast, and at the same time, inhibits the growth of nitrite. The acidic environment produced by the movement of the lactic acid bacteria and the Weissella gradually degrades the nitrite. Compared with the prior art, not only can the growth of miscellaneous bacteria in the fermentation of the pickled vegetable be inhibited, and the pickled vegetable "flowering" be avoided, but also the safety and sensory quality of the pickled vegetable are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food processing, in particular to a pickled vegetable and a preparation method thereof. BACKGROUND

[0002] The pickled vegetable is a fermented food produced by pickling fresh vegetables with low-concentration brine, seasoning, packaging, sterilization and other processes. However, the raw materials of the pickled vegetable are not sterilized, or the oxygen is not well isolated during the fermentation and storage stage, which leads to the growth of yeast, or after the same mother liquor is used for fermentation for many times, a white film in the form of pieces or petals will be formed on the interface of the pickled vegetable liquid, which is called "flowering". Once the pickled vegetable "flowers", the flavor of the pickled vegetable deteriorates, such as producing rancid smell or putrefactive smell, and the pickled vegetable becomes soft and rotten, and the pickled vegetable liquid becomes turbid.

[0003] The pickled vegetable "flowering" phenomenon is common, whether in the pickled vegetable made at home or in commercial products, different degrees of "flowering" phenomenon often occur, which is generally treated by timely separating the white flower and adding liquor and other bacteriostatic substances, which is complicated and easy to "flower" again. In industry, additives are often used to inhibit flowering, which affects the safety of the pickled vegetable. Therefore, it is necessary to provide a pickled vegetable preparation method which can inhibit bacteria for a long time and is safe. SUMMARY

[0004] Based on the above reasons, one of the purposes of the present application is to provide a pickled vegetable and a preparation method thereof, which can inhibit the "flowering" of the pickled vegetable by controlling the oxygen content and inhibiting the growth of miscellaneous bacteria; and the second purpose is to provide a pickled vegetable with low nitrite content, which can improve the safety of the pickled vegetable.

[0005] The first technical solution of the present application provides a preparation method of a pickled vegetable, comprising:

[0006] The pickled vegetable mother liquor containing oligosaccharides and mint extract is prepared, a complex bacterial inoculum composed of lactic acid bacteria and Weissella is inoculated into the pickled vegetable mother liquor, and the inoculated pickled vegetable mother liquor is injected into the pretreated fresh vegetables for fermentation.

[0007] Further, the oligosaccharides are non-reducing oligosaccharides.

[0008] Preferably, the oligosaccharides are xylo-oligosaccharides and / or isomalto-oligosaccharides.

[0009] Further, the water used in the pickled vegetable mother liquor is sterile water, and the mass ratio of sterile water, oligosaccharides and mint extract is 100: (2-8): (0.5-1.0).

[0010] Further, the lactic acid bacteria are facultative anaerobic lactobacillus, and the mass ratio of lactic acid bacteria and Weissella is 1: (1-2).

[0011] Preferably, the lactobacillus is Lactobacillus acidophilus and / or Lactobacillus plantarum; the weissella is Weissella cibaria.

[0012] Further, the inoculation amount of the complex bacterial agent is 0.05-0.15% of the mass of the pickled vegetable mother water.

[0013] Further, the fermentation is anaerobic fermentation at 4-35℃.

[0014] Further, the complex bacterial agent further comprises Leuconostoc, and when added to the pickled vegetable mother water, the mass ratio of the lactobacillus, the weissella and the Leuconostoc is 1:(1-2):(1-2).

[0015] The application also provides a pickled vegetable prepared according to the above pickled vegetable preparation method.

[0016] The application has the following beneficial effects:

[0017] 1. In the preparation method of the multi-strain complex fermented pickled vegetable, the lactobacillus consumes oxygen in the pickled vegetable jar, the oligosaccharide selectively proliferates the weissella, the generated carbon dioxide can promote the rapid formation of an anaerobic environment, and the three work together to accelerate the creation of an anaerobic environment. In the process of forming the anaerobic environment, the yeast can still move, and the activity of the lactobacillus can produce bacteriostatic substances, but the inhibitory effect is weak. Therefore, the addition of the mint extract improves the bacteriostatic effect of the yeast. By controlling the content of oxygen and adding the mint extract to inhibit the growth of miscellaneous bacteria, the "flowering" of the pickled vegetable can be effectively inhibited.

[0018] 2. The application inhibits the formation of nitrosamine and reduces the peak value of nitrite through the mint extract in the fermentation process. The weissella is proliferated by the oligosaccharide, the acid production is promoted, the formation of an acidic environment is accelerated, the nitrite is degraded, and the safety of the pickled vegetable is improved.

[0019] 3. The application reduces the rate of pH decrease in the fermentation environment through the mint extract, reduces the amount of acid generated in the late fermentation stage through the oligosaccharide, and then slows down the discoloration process and the change in texture of the pickled vegetable, thereby improving the sensory quality of the finished pickled vegetable. DETAILED DESCRIPTION

[0020] The scheme of the application will be explained below in conjunction with the examples. Those skilled in the art will understand that the following examples are only used to illustrate the application and should not be regarded as limiting the scope of the application. In the examples, the techniques or conditions that are specifically mentioned are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments that are not mentioned by the manufacturer are all conventional products that can be obtained from the market.

[0021] The application is based on the problem that traditional pickled vegetable fermentation is easy to produce flower, by inoculating lactobacillus to consume oxygen in the pickled vegetable jar, and adding oligosaccharide, the weissella can become the dominant bacteria in the early fermentation, and the heterotypic lactic acid fermentation is carried out, the generated carbon dioxide can promote the rapid formation of anaerobic environment, and the flavor of the pickled vegetable with rich components such as ethanol and acetic acid is also generated, the lactobacillus, oligosaccharide and weissella can cooperate to accelerate the creation of anaerobic environment, in the process of forming anaerobic environment, the yeast can still move, and the lactobacillus can produce bacteriostatic substances, but the inhibition effect is weak, so the bacteriostatic effect of the yeast is improved by adding mint extract; the mint extract can also effectively reduce the content of nitrite in the pickled vegetable, on the other hand, the activity of lactobacillus and weissella accelerates the fermentation process, and the formed acidic environment makes the nitrite begin to degrade, the common action of the mint extract, lactobacillus and weissella reduces the content of nitrite in the pickled vegetable, and ensures the safety of the pickled vegetable.

[0022] In order to facilitate the understanding of the design idea of the application, first, the key process in the pickled vegetable production process is briefly described: the processing of pickled vegetable is generally divided into raw material selection, pretreatment, mother water preparation and jar fermentation.

[0023] Among them, the pretreatment step is the treatment of raw materials, which prevents the raw materials from bringing in raw water, and the raw water contains many impurities and many bacteria, which will affect the fermentation quality if brought into the fermentation jar; the second is the sterilization treatment of the fermentation jar to avoid bacterial contamination; the purpose of the above two steps is to prevent the fermentation mother liquor from being contaminated by bacteria and to avoid the pickled vegetable "flowering".

[0024] Among them, the mother water preparation is a crucial step in the fermentation of pickled vegetable, and the mother water has the functions of flavoring, removing excess water, shaping and sterilizing the food materials (vegetables), and is also called brine because the main raw material is salt.

[0025] Among them, the jar fermentation is the key to the maturity of pickled vegetable, and attention should be paid to the isolation of oxygen during the fermentation process, and many scholars have proved that the main bacteria of "flowering" is yeast, under the stimulation of air, the genes with the functions of synthesizing protein and phospholipid in the yeast change, have a significant influence on ribosome pathway and fatty acid synthesis pathway, and change the up-regulation of genes in the two pathways, which is beneficial to the production of protein and phospholipid, thereby leading to "flowering"; therefore, attention should be paid to the isolation of oxygen during the fermentation process of pickled vegetable.

[0026] During the fermentation of pickles, the change of nitrite is generally as follows: in the initial stage of fermentation, there is oxygen in the fermentation jar, the activity of lactic acid bacteria is inhibited, and the lactic acid produced by lactic acid bacteria is small, under the action of nitrate reducing bacteria, the content of nitrite increases; in the middle stage of fermentation, the content of nitrite accumulates and increases to the maximum, lactic acid bacteria inhibit the growth and reproduction of other bacteria, the pH value decreases, the growth and reproduction of nitrate reducing bacteria are inhibited, at the same time, part of the nitrite is decomposed; in the later stage of fermentation, the content of nitrite decreases, lactic acid continues to accumulate to the maximum, the pH value continues to decrease, the growth and reproduction of nitrate reducing bacteria are inhibited, the pH value continues to decrease to a relatively stable value, and the growth and reproduction of nitrate reducing bacteria are completely inhibited, most of the nitrite is decomposed; with the extension of fermentation time, the nitrate in the vegetables is easily reduced to nitrite by the nitrate reducing bacteria, and the content of nitrite increases again, the content of nitrite will change due to the strength of the activity of microorganisms in the fermentation liquor.

[0027] The first embodiment of the present application provides a preparation method of pickles, comprising: preparing a pickle mother liquor containing oligosaccharides and mint extract, inoculating a complex microbial inoculant composed of lactic acid bacteria and weissella into the pickle mother liquor, and injecting the inoculated pickle mother liquor into pretreated fresh vegetables for fermentation.

[0028] It should be noted that lactic acid bacteria is an anaerobic or facultative anaerobic microorganism, in this embodiment, the added lactic acid bacteria is facultative anaerobic lactobacillus, which aims to consume the oxygen in the pickle jar at the beginning of fermentation, create an anaerobic environment, and prevent the growth and reproduction of yeast belonging to the genus of “flowering bacteria”; at the same time, the activity of lactobacillus can produce bacteriostatic substances to inhibit the growth and activity of yeast.

[0029] It should be noted that when fresh vegetables are placed in the fermentation jar for fermentation, some miscellaneous bacteria will inevitably be brought in, and the oxygen existing in the fermentation jar in the initial stage of fermentation will be conducive to the growth and reproduction of miscellaneous bacteria such as yeast, resulting in weak growth and activity of beneficial bacteria in pickles in the early stage of fermentation, and further leading to “flowering” of pickles.

[0030] In view of the above problems, the present application improves the bacteriostatic effect by adding mint extract to the mother liquor. The main components of mint extract are levomint and flavonoids, which have strong antioxidant properties, so they have good bacteriostatic effect; on the other hand, the synthesis of nitrosamine is hindered by mint extract, which eliminates nitrite and improves the safety of pickles while giving pickles a cool taste; at the same time, the polyhydroxy structure contained in the mint extract may inhibit the generation of lactic acid in the pickle fermentation mother liquor by reacting with hydrogen ions in the pickle fermentation mother liquor, slow down the rate of pH value reduction, and have a positive effect on the protection of the color and taste of pickles.

[0031] It should be noted that in the early stage of fermentation, due to the large reproduction of microorganisms, the metabolic rate is relatively slow, and the fermentation process is relatively slow, therefore, the addition of oligosaccharides can accelerate the fermentation process. The effect of adding oligosaccharides is to proliferate lactic acid bacteria, accelerate the fermentation process, and inhibit the activity of miscellaneous bacteria.

[0032] In some specific embodiments, the oligosaccharide is a non-reducing oligosaccharide, including but not limited to sucrose, maltose, lactose, cellobiose, trehalose, raffinose, fructooligosaccharide, xylooligosaccharide, isomaltooligosaccharide, and cyclodextrin. Non-reducing oligosaccharides not only increase the value of lactic acid bacteria, but also reduce the amount of acid generated. In the later stage of fermentation, the available glucose content in the pickled vegetable mother water is reduced, and the oligosaccharide is usually connected by glycosidic bond 2-4 monosaccharides into small oligomers, which is easier to be decomposed in the fermentation process, and the content gradually increases. The utilization rate of non-reducing sugar by lactic acid bacteria is low, the generation of acid is reduced, and the pH in the later stage of fermentation is delayed, which has a positive effect on the protection of the color and taste of pickles.

[0033] In some preferred embodiments, the oligosaccharide is xylooligosaccharide and / or isomaltooligosaccharide, wherein: xylooligosaccharide is an oligosaccharide composed of xylose units, which is a mixture of oligosaccharides. In the fermentation process, xylobiose and xylotriose are decomposed by microorganisms to generate xylose. Xylooligosaccharide not only selectively proliferates Weissella, making it become the dominant genus in anoxic environment, but also reduces the amount of acid generated. On the other hand, xylooligosaccharide can promote the proliferation of Weissella, and the generated acidic environment starts to decompose nitrite, reducing the nitrite content in pickles and improving the safety of pickles. Isomaltooligosaccharide can selectively proliferate Lactobacillus acidophilus, rapidly consume oxygen in the early stage of fermentation, accelerate the fermentation process, and inhibit the peak of nitrite, thereby reducing the content of nitrite and improving the safety of pickles.

[0034] In some preferred embodiments, the water used for the pickled vegetable mother water is sterile water, and the mass ratio of sterile water, oligosaccharide, and mint extract is 100: (2-8): (0.5-1.0).

[0035] In some specific embodiments, the lactic acid bacteria include but are not limited to Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus casei, Lactobacillus acidophilus, and Lactobacillus plantarum. In some preferred embodiments, the lactic acid bacteria are Lactobacillus acidophilus and / or Lactobacillus plantarum, which can grow and reproduce well in anoxic environment, form dominant bacteria in the early stage of fermentation, consume oxygen in the fermentation jar, and generate lactic acid.

[0036] In some preferred embodiments, the Weissella is Weissella paramesenteroides, which not only can accelerate the formation of anaerobic environment and enrich the flavor of pickles, but also can produce beneficial bioactive substances during fermentation, which can be used to improve the quality of pickles and the safety of fermentation process.

[0037] In some specific embodiments, the fermentation conditions are anaerobic fermentation at 4-35°C, and the complex microbial agent in the present application is all lactic acid bacteria, most of which are anaerobic microorganisms that can better survive in anoxic environment. The presence of oxygen can stimulate the growth of yeast, leading to the formation of "flowers" in pickles and affecting the quality. Therefore, in order to ensure the quality of fermentation, anaerobic fermentation is required during fermentation, and the pickle mother water should cover the fresh vegetables to be pickled.

[0038] In some specific embodiments, the complex microbial agent further comprises Leuconostoc, and when Leuconostoc is included, the complex microbial agent has a mass ratio of 1: (1-2): (1-2) of Lactobacillus, Weissella, and Leuconostoc. It should be noted that the purpose of adding Leuconostoc is to increase the characteristic flavor of pickles.

[0039] In some specific embodiments, sterile water can be obtained by boiling and cooling water. Boiling water can kill microorganisms in water and reduce minerals in water, achieving the effects of sterilization and impurity removal. Cooling the water is to avoid killing the inoculated complex microbial agent due to high temperature.

[0040] In some specific embodiments, the fresh vegetables to be pickled need to be selected, washed, cut, and dried to prevent the entry of raw water and cause bacterial contamination, affecting the quality of pickles.

[0041] In some specific embodiments, the preparation of pickle mother water further comprises adding other seasoning spices, such as salt, Sichuan pepper, white wine, and chili.

[0042] The second embodiment of the present application provides pickles obtained according to the above-mentioned preparation method of pickles.

[0043] It should be noted that the obtained pickles have lower nitrosamine content due to the inhibition of the synthesis of nitrosamine in pickles by the peppermint extract, and the reduction of the peak value of nitrite. In addition, the fermentation process is accelerated by the action of oligosaccharides, Lactobacillus, and Weissella, and the nitrite formed in the early stage of pickles is rapidly degraded in the rapidly formed acidic environment. The combined action of the four greatly reduces the content of nitrite in the finished pickles, making the pickles safer. On the other hand, under the action of the peppermint extract and oligosaccharides, the pH reduction rate of pickles during fermentation is slowed down, and the pH value of pickles is increased, which is more conducive to the protection of the color and texture of pickles, and improves the sensory quality of the finished pickles.

[0044] It can be understood that, in addition to the above special instructions, other parameters of the embodiments of the present application can be obtained by experiments according to general experience or actual needs of those skilled in the art, and the present application does not make special limitations, and only provides some preferred embodiments, for example, in some preferred embodiments, the inoculation amount of the complex bacterial species is 0.05-0.15% of the mass of the pickled vegetable mother water; in some preferred embodiments, the mass ratio of lactobacillus to weissella is 1: (1-2).

[0045] The following will disclose specific examples for implementing the present application, and the corresponding comparative examples will prove the technical effects related to the present application.

[0046] Example 1: Preparation of pickled vegetables

[0047] 1. Raw material pretreatment: select fresh mustard without yellow leaves and rotten leaves, wash, trim, and dry the surface moisture;

[0048] 2. Preparation of pickled vegetable mother water: add 0.4 kg of xylo-oligosaccharides, 0.08 kg of mint extract, 0.8 kg of salt, 0.7 kg of white wine, 0.1 kg of old ginger, 0.2 kg of small chili peppers, 0.05 kg of Sichuan pepper to 10 kg of sterile water, and mix evenly;

[0049] 3. Inoculation: inoculate 12.33 g of complex bacterial agent (5 g of Lactobacillus acidophilus and 10 g of Weissella paramesenteroides mixed) into the pickled vegetable mother water, and mix evenly;

[0050] 4. Fermentation in jars: pack the mustard into a pickled vegetable jar, pour the inoculated pickled vegetable mother water, and the mother water covers the mustard, and ferment in an environment of 25℃ for 7 days.

[0051] Example 2: Preparation of pickled vegetables

[0052] 1. Raw material pretreatment: select fresh and disease-free carrots and white radishes, remove the celery stems, wash, trim, and dry the surface moisture;

[0053] 2. Preparation of pickled vegetable mother water: add 0.3 kg of xylo-oligosaccharides, 0.05 kg of mint extract, 0.6 kg of salt, 0.4 kg of white wine, 0.1 kg of old ginger, 0.2 kg of small chili peppers, 0.05 kg of star anise, and 0.05 kg of Sichuan pepper to 10 kg of sterile water, and mix evenly;

[0054] 3. Inoculation: inoculate 17.63 g of complex bacterial agent (9 g of Lactobacillus plantarum and 9 g of Weissella paramesenteroides mixed) into the pickled vegetable mother water, and mix evenly;

[0055] 4. Fermentation in jars: pack the vegetables to be pickled into a pickled vegetable jar, pour the inoculated pickled vegetable mother water, and the mother water covers the vegetables to be pickled, and ferment in an environment of 35℃ for 5 days.

[0056] Example 3 Preparation of pickled vegetable

[0057] 1. Raw material pretreatment: select fresh choy sum without yellow leaves and rotten leaves, remove the stem of fresh green pepper, wash, trim, and dry the surface moisture;

[0058] 2. Preparation of pickled vegetable mother liquor: add 0.6 kg of isomaltooligosaccharide, 0.1 kg of mint extract, 0.7 kg of salt, 0.7 kg of white wine, 0.1 kg of old ginger, 0.05 kg of garlic, 0.2 kg of small chili pepper, 0.05 kg of pepper, and 0.05 kg of cassia to 10 kg of sterile water and mix well;

[0059] 3. Inoculation: inoculate 15.0 g of complex microbial inoculant (6 g of Lactobacillus acidophilus and 9 g of Weissella cibaria) into the pickled vegetable mother liquor and mix well;

[0060] 4. Fermentation in jar: put the vegetables to be pickled into a pickled vegetable jar, pour the inoculated pickled vegetable mother liquor, and the mother liquor covers the vegetables to be pickled, and then ferment in an environment of 28℃ for 4 days.

[0061] Example 4 Preparation of pickled vegetable

[0062] 1. Raw material pretreatment: select fresh cowpea without insect pests, wash, trim, and dry the surface moisture;

[0063] 2. Preparation of pickled vegetable mother liquor: add 0.5 kg of salt, 0.3 kg of white wine, 0.2 kg of xylo-oligosaccharide, 0.05 kg of mint extract, 0.1 kg of old ginger, 0.05 kg of garlic, 0.2 kg of small chili pepper, 0.05 kg of pepper, and 0.01 kg of star anise to 10 kg of sterile water and mix well;

[0064] 3. Inoculation: inoculate 11.5 g of complex microbial inoculant (4 g of Lactobacillus plantarum, 4 g of Leuconostoc mesenteroides, and 4 g of Weissella cibaria) into the pickled vegetable mother liquor and mix well;

[0065] 4. Fermentation in jar: put the cowpea into a pickled vegetable jar, pour the inoculated pickled vegetable mother liquor, and the mother liquor covers the cowpea, and then ferment in an environment of 4℃ for 10 days.

[0066] Example 5 Preparation of pickled vegetable

[0067] 1. Raw material pretreatment: select fresh asparagus lettuce and garlic sprouts without insect pests, wash, cut into strips, and dry the surface moisture;

[0068] 2. Preparation of pickled vegetable mother liquor: add 0.4 kg of salt, 0.5 kg of white wine, 0.8 kg of isomaltooligosaccharide, 0.01 kg of mint extract, 0.1 kg of old ginger, 0.2 kg of small chili pepper, 0.05 kg of pepper, and 0.01 kg of white vinegar to 10 kg of sterile water and mix well;

[0069] 3. Inoculation: 12 g of complex microbial inoculant (3 g of Lactobacillus acidophilus, 6 g of Leuconostoc mesenteroides subsp. dextranicum, and 3 g of Weissella cibaria) was inoculated into the pickled vegetable mother liquor and mixed evenly;

[0070] 4. Jar fermentation: The radish strips were placed in a pickled vegetable jar, the inoculated pickled vegetable mother liquor was poured in, the mother liquor covered the radish strips, and fermentation was carried out at 30°C for 3 days.

[0071] Preparation of pickled vegetables in Comparative Example 1

[0072] The preparation method was the same as in Example 1, except that Comparative Example 1 did not add xylooligosaccharides.

[0073] Preparation of pickled vegetables in Comparative Example 2

[0074] The preparation method was the same as in Example 1, except that Comparative Example 2 did not add mint extract.

[0075] Preparation of pickled vegetables in Comparative Example 3

[0076] The preparation method was the same as in Example 1, except that Comparative Example 3 replaced Lactobacillus acidophilus with an equal amount of Lactobacillus rhamnosus (anaerobic lactobacillus).

[0077] Preparation of pickled vegetables in Comparative Example 4

[0078] The preparation method was the same as in Example 1, except that Comparative Example 4 did not inoculate Weissella cibaria, but inoculated 12.33 g of Lactobacillus acidophilus.

[0079] Test Example 1: Observation of flower growth

[0080] Test method: 30 food professionals with normal vision were selected, and the pickled vegetables of Examples 1-5, Comparative Examples 1-3, and the control group (natural fermentation) were observed for flower growth by color observation, and the results were recorded. "-" indicates that there is no white flower on the interface of the pickled vegetables; "+" indicates that there are a small amount of white flowers on the interface of the pickled vegetables; "++" indicates that there are more white flowers on the interface of the pickled vegetables.

[0081] Test results: see Table 1. Since there was no "flower growth" phenomenon in the early stage of observation of the experimental samples, the experimental results only listed the number of days when each sample changed.

[0082] Result analysis: from table 1, it can be seen that the comparative example 2 (canceling the addition of mint extract) began to appear white flowers at the 15th day of fermentation, the comparative example 1 (canceling the addition of xylo-oligosaccharide) and the comparative example 4 (canceling the inoculation of weissella cibaria) began to appear white flowers at the 23rd day of fermentation, the comparative example 3 (replacing lactobacillus acidophilus with lactobacillus rhamnosus) began to appear white flowers at the 25th day of fermentation, and the examples 1-5 all began to appear white flowers after 50 days of fermentation, while the control group (natural fermentation) appeared white flowers at the 7th day of fermentation, indicating that mint extract, oligosaccharide, lactobacillus and weissella can all affect the "flowering" of pickles, and the four together can better inhibit the effect.

[0083] Table 1 observation results of flowering

[0084] .

[0085] Test example 2 bacteriostatic experiment

[0086] Experimental method: the white film of the pickles was picked up with a sterile glass rod, which covered more than 1 cm of one end of the glass rod, and was placed in a 10 mL sterile physiological saline test tube for dilution, and then the dilution liquid was cultured on a bengal red culture medium. Finally, 7 strains (J1, J2, J3, J4, J5, J6, J7) were selected for activation culture on PDA culture medium for 2 times, and a bacteriostatic experiment was performed. After the PDA (yeast) culture medium prepared and cooled to 45℃, 2% of the above activated bacterial liquid was added, and the culture medium was poured into a blank sterilized flat plate at 15 mL. After the culture medium was cooled, 4 symmetrical holes were punched with a sterile oxford cup (inner diameter 6 mm), and the sterilized oxford cup was placed on the flat plate at four symmetrical points. 200 μL of pickle mother liquor of examples 1-3 and comparative examples 1-3 was added to the oxford cup with a pipette, and MRS liquid medium was added to the oxford cup as a control. After 48 h of culture in a 30℃ constant temperature incubator, the size of the bacteriostatic ring was recorded.

[0087] Experimental results: see table 2.

[0088] Result analysis: from table 2, it can be seen that the pickle mother liquor of examples 1-5 has good bacteriostatic effect, indicating that the technical means of the present application can effectively inhibit the growth of miscellaneous bacteria in pickles; compared with example 1, the bacteriostatic effect of comparative example 1 (canceling the addition of xylo-oligosaccharide), comparative example 3 (replacing lactobacillus acidophilus with lactobacillus rhamnosus) and comparative example 4 (canceling the inoculation of weissella cibaria) is poor, indicating that rapid reduction of oxygen content can effectively inhibit the growth of yeast; compared with example 1, the bacteriostatic effect of comparative example 2 (canceling the addition of mint extract) is significantly reduced, indicating that mint extract has good bacteriostatic effect on yeast.

[0089] Table 2 bacteriostatic experiment results of pickle mother liquor

[0090] .

[0091] Note: Inhibition zone diameter 5-10 mm: +; 10-15 mm: ++; > 15 mm: +++; No inhibition zone: -

[0092] Experimental Example 3 Determination of Nitrite Content

[0093] Experimental method: The nitrite content was determined according to GB 5009.33-2016 Spectrophotometric method for determination of nitrite and nitrate in food.

[0094] Experimental results: See Table 3.

[0095] Result analysis: As can be seen from Table 3, compared with Example 1, the appearance of the peak value of nitrite in Comparative Example 1 (without adding xylo-oligosaccharides) is later, indicating that xylo-oligosaccharides can accelerate the fermentation process and thus reduce the content of nitrite; the content of nitrite in Comparative Example 2 (without adding mint extract) is significantly increased, indicating that the addition of mint extract can effectively inhibit the synthesis of nitrosamine and thus reduce the peak value of nitrite; the peak value in Comparative Example 3 (without inoculating Lactobacillus acidophilus) appears later, indicating that Lactobacillus acidophilus can accelerate the lactic acid fermentation process; the peak value of nitrite in Comparative Example 4 (without inoculating Weissella) appears late, and the content of nitrite is high in the later fermentation stage, indicating that Weissella is beneficial to accelerate the fermentation process and has a positive effect on the degradation of nitrite; in summary, in the present application, in the early stage of fermentation, the pickle jar contains oxygen, and the growth of nitrate-reducing bacteria increases the content of nitrite in the pickle, after the oxygen is consumed, the lactic acid bacteria activity causes the pH to drop, and the lactic acid, acetic acid and other substances produced begin to degrade nitrite, and the content of nitrite gradually decreases, among which the mint extract can reduce the content of nitrite, xylo-oligosaccharides and Lactobacillus acidophilus can accelerate the formation of lactic acid, so that the nitrite is degraded in advance, and Weissella can accelerate the fermentation process and degrade the generated nitrite, and the active substances produced by the metabolic activity can inhibit the synthesis of nitrite, the synergistic effect of the four can reduce the generation of nitrite and degrade nitrite, thereby significantly reducing the content of nitrite and improving the safety of pickles.

[0096] Table 3 Experimental results of changes in nitrite content during pickle fermentation

[0097] .

[0098] Test Example 4 Sensory Test

[0099] Experimental method: 30 food professionals with normal taste and vision were selected, and the pickles of Example 1, Comparative Examples 1-3 and the control group (natural fermentation) were evaluated by tasting and color observation, and the results were recorded.

[0100] Experimental results: see Table 4.

[0101] Result analysis: from Table 4, compared with Example 1, the pickles of the control group were obviously browned, and the texture was greatly changed. The pickles of Comparative Example 1 (without adding xylo-oligosaccharides) and Comparative Example 2 (without adding mint extract) were both browned in color, and the texture was soft, and the taste was sour and soft. This was because the change of pH would change the enzyme activity in mustard, and with the change of the acidic environment, the discoloration of mustard would undergo a discoloration process of green-yellow green-light yellow-golden yellow-yellow brown-brown. In Example 1, Comparative Example 3 and Comparative Example 4, both xylo-oligosaccharides and mint extract were present, and the synergistic effect of the two slowed down the rate of pH decrease in the environment, and the color change of mustard was also slow. At the same time, the cross-linking degree of cellulose and hemicellulose in mustard was also well maintained, so it had a good sensory effect. In summary, the main reason affecting the sensory of pickles is the addition of xylo-oligosaccharides and mint extract, which in turn affects the activity of microorganisms. The single effect of xylo-oligosaccharides and mint extract on the change of pickle quality has a certain positive effect, and the combination of the two can significantly improve the sensory quality of pickles.

[0102] Table 4 Sensory evaluation results

[0103] .

[0104] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing kimchi, characterized by, The application relates to a pickled vegetable preparation method. The pickled vegetable mother liquor containing non-reducing oligosaccharides and mint extract is prepared, a composite microbial inoculum composed of lactic acid bacteria and Weissella is inoculated into the pickled vegetable mother liquor, and the inoculated pickled vegetable mother liquor is injected into pretreated fresh vegetables to perform fermentation. The lactic acid bacteria are facultative anaerobic lactobacillus, and the mass ratio of the lactic acid bacteria to the Weissella is 1: (1-2). The oligosaccharides are xylo-oligosaccharides and / or isomalto-oligosaccharides. The water used in the pickled vegetable mother liquor is sterile water, and the mass ratio of the sterile water, the oligosaccharides and the mint extract is 100: (2-8): (0.5-1.0). The inoculation amount of the composite microbial inoculum is 0.05-0.15% of the mass of the pickled vegetable mother liquor.

2. The production method according to claim 1, characterized by, The lactic acid bacteria are Lactobacillus acidophilus and / or Lactobacillus plantarum, and the Weissella is Weissella paramesenteroides.

3. The preparation method according to claim 1, characterized in that, The fermentation is anaerobic fermentation at 4-35 DEG C.

4. A method for preparing kimchi, characterized by, The application relates to a pickled vegetable preparation method. The pickled vegetable mother liquor containing non-reducing oligosaccharides and mint extract is prepared, a composite microbial inoculum composed of lactic acid bacteria and Weissella is inoculated into the pickled vegetable mother liquor, and the inoculated pickled vegetable mother liquor is injected into pretreated fresh vegetables to perform fermentation. The lactic acid bacteria are facultative anaerobic lactobacillus, and the mass ratio of the lactic acid bacteria to the Weissella is 1: (1-2). The oligosaccharides are xylo-oligosaccharides and / or isomalto-oligosaccharides. The water used in the pickled vegetable mother liquor is sterile water, and the mass ratio of the sterile water, the oligosaccharides and the mint extract is 100: (2-8): (0.5-1.0). The inoculation amount of the composite microbial inoculum is 0.05-0.15% of the mass of the pickled vegetable mother liquor.

5. The preparation method according to claim 4, characterized in that, The lactic acid bacteria are Lactobacillus acidophilus and / or Lactobacillus plantarum, and the Weissella is Weissella paramesenteroides.

6. The preparation method according to claim 4, characterized in that, The fermentation is anaerobic fermentation at 4-35 DEG C.

7. A pickled vegetable prepared by the preparation method according to any one of claims 1-6.