Complex microbial inoculant for preparing pickled Chinese cabbages by fermenting clear soybean water and fermentation method

Abstract

The invention provides a complex microbial inoculant for preparing pickled Chinese cabbages by fermenting clear soybean water and a fermentation method, and belongs to the technical field of fermented foods. The complex microbial inoculant for preparing the pickled Chinese cabbages by fermenting the soybean clear water comprises the following strains in percentage by mass: 40-60% of lactobacillus plantarum, 20-35% of lactobacillus acidophilus, 10-25% of saccharomyces cerevisiae and 5-15% of bacillus acidophilus. Pretreated bean clear water is used as a fermentation substrate, the complex microbial inoculant is inoculated for fermentation to prepare the pickled Chinese cabbage, the fermentation period is shortened, the fermentation quality of the pickled Chinese cabbage is improved, the safety of the pickled Chinese cabbage is guaranteed, the pickled Chinese cabbage is endowed with special bean fragrance, and resource utilization of the bean clear water is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of fermented foods, and in particular relates to a composite bacterial agent for preparing sauerkraut by fermenting soy and water, and a fermentation method. Background Art

[0002] Traditional sauerkraut is typically fermented using water or low-concentration saltwater, relying on natural lactic acid bacteria to ferment naturally. While this method is cost-effective, it suffers from significant drawbacks: Traditional sauerkraut relies primarily on the vegetable's own components and salt, lacking exogenous functional active substances and limiting its nutritional value. The naturally fermented bacterial flora is complex and susceptible to contamination by other bacteria, resulting in large fluctuations in nitrite levels, long fermentation cycles, and poor flavor stability.

[0003] In the soybean deep processing industry, soy water is a by-product of the tofu molding process, with an annual output of up to millions of tons. Soy water is rich in active ingredients such as soybean oligosaccharides, small molecule peptides and isoflavone glycosides, but it is currently mainly treated as high-COD wastewater, with extremely low resource utilization rate, causing serious environmental burden and economic losses. In recent years, there have been no reports on the direct use of soy water as a fermentation matrix for sauerkraut preparation. In addition, existing sauerkraut fermentation technologies focus more on improving bacterial agents (such as shortening the fermentation cycle or reducing nitrite), but ignore improving the functionality of sauerkraut through matrix innovation.

[0004] Therefore, developing an efficient fermentation process based on soy water, making full use of its functional ingredients, and simultaneously realizing the resource utilization of soy water and upgrading the quality of sauerkraut has become a technical problem that the industry urgently needs to break through. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a composite bacterial agent and a fermentation method for preparing sauerkraut by fermenting soy bean water, so as to realize resource utilization of soy bean water and improve the fermentation quality of sauerkraut.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A composite bacterial agent for preparing sauerkraut by fermenting soy water comprises the following bacterial species in the following mass percentages: 40-60% of Lactobacillus plantarum, 20-35% of Lactobacillus acidophilus, 10-25% of Saccharomyces cerevisiae and 5-15% of Bacillus acidophilus.

[0008] Preferably, the preparation method comprises the following steps: (1) respectively carrying out liquid expansion culture of Lactobacillus plantarum, Lactobacillus acidophilus, Saccharomyces cerevisiae and Bacillus acidophilus until the number of viable cells is ≥1×10 9 CFU / mL; (2) mixing the bacterial solution obtained in step (1) in proportion and adding a lyophilization protective agent; (3) freeze-drying the mixture to prepare a powder, vacuum-packing and storing at 4-10°C.

[0009] The present invention also provides application of the composite bacterial agent in preparing sauerkraut.

[0010] The present invention also provides a method for preparing sauerkraut by fermenting soy bean water, comprising the following steps: (1) sterilizing the soy bean water, adjusting the pH to 5.0-6.5 and the salt concentration to 2-3%, wherein the soy bean water is waste liquid after pulping and forming in the tofu production process; (2) inoculating the composite bacterial agent into the soy bean water, and activating and culturing for 1-2 hours; and (3) mixing the pre-salted and dehydrated vegetables with the soy bean water in step (2), and fermenting to prepare sauerkraut.

[0011] Preferably, the temperature for sterilizing the soy milk is 80-90° C. and the time is 10-30 min; and food-grade sodium bicarbonate or citric acid is used to adjust the pH.

[0012] Preferably, the inoculation amount of the composite bacterial agent is 0.1-0.5% of the mass of the soy water.

[0013] Preferably, the activation culture temperature is 25-30°C.

[0014] Preferably, the vegetables are mixed with soy and water in a mass ratio of 1:1-2, and the vegetables are compacted until they are completely immersed.

[0015] Preferably, the fermentation is carried out by staged temperature control: fermentation at 20-28°C for 3-5 days, fermentation at 15-20°C for 5-15 days, and fermentation to pH ≤ 4.2.

[0016] The invention also provides sauerkraut prepared by the fermentation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The composite bacterial agent of this invention has synergistic functions, specifically improving fermentation efficiency and quality. By optimizing the bacterial strain ratio, this invention achieves synergistic effects in acid production, flavor generation, and macromolecular degradation, significantly shortening the fermentation cycle and ensuring a pH of ≤4.2 at the fermentation endpoint, thereby inhibiting contamination by other bacteria.

[0019] The present invention can realize resourceful utilization of soy water and impart functional ingredients to sauerkraut. The invention converts soy water from tofu production into a fermentation medium, replacing traditional brine, reducing wastewater discharge and raw material costs. Soy water is rich in active ingredients such as soy oligosaccharides (such as stachyose), small molecule peptides, and isoflavone glycosides. After fermentation, it significantly enhances the nutritional value and functionality of sauerkraut and imparts its distinctive bean flavor. DETAILED DESCRIPTION

[0020] The present invention provides a composite bacterial agent for preparing sauerkraut by fermenting soy water, comprising the following bacterial strains in the following mass percentages: 40-60% Lactobacillus plantarum, 20-35% Lactobacillus acidophilus, 10-25% Saccharomyces cerevisiae, and 5-15% Bacillus acidophilus; more preferably, 45-55% Lactobacillus plantarum, 22-30% Lactobacillus acidophilus, 12-20% Saccharomyces cerevisiae, and 8-12% Bacillus acidophilus; and more preferably, 50% Lactobacillus plantarum, 25% Lactobacillus acidophilus, 15% Saccharomyces cerevisiae, and 10% Bacillus acidophilus. The present invention has no particular limitation on the source of the bacterial strains, and commonly used strains in the technical field can be selected. As an embodiment, the Lactobacillus plantarum of the present invention is numbered CGMCC No. 31144; the Lactobacillus acidophilus is numbered CICC 6093; the Saccharomyces cerevisiae is numbered CICC 1406; and the Bacillus sp is Bacillus siamese CD92-3.

[0021] In the composite bacterial agent of the present invention, Lactobacillus plantarum utilizes the soluble sugars in the soy water to quickly generate lactic acid in the early stage of fermentation, lower the pH of the fermentation environment, inhibit the proliferation of spoilage bacteria, and metabolize to produce volatile substances such as ethyl acetate and diacetyl, laying the "fresh and fragrant" tone of sauerkraut. Lactobacillus acidophilus continues to produce acid in the middle and late stages of fermentation, further lowering the pH of the fermentation environment, thoroughly inhibiting miscellaneous bacteria, while degrading anti-nutritional factors such as phytic acid and tannins, and improving the nutrient utilization rate of soy water. The extracellular polysaccharides it secretes can also enhance the viscoelasticity of sauerkraut and alleviate the problem of excessive softening. Saccharomyces cerevisiae can produce higher alcohols and esters, giving sauerkraut a "fruity" and "wine-like" aroma. It can also consume residual oxygen and promote anaerobic fermentation dominated by lactic acid bacteria. Its autolysis releases amino acids, enhancing the umami taste. Acidophilic Bacillus secretes proteases and cellulases, breaking down glycinin and cellulose in the soy water into small peptides and soluble sugars in an acidic environment. This provides fast-acting nutrition for lactic acid bacteria and yeast. It also secretes pectinase to target and degrade the extracellular matrix, maintaining a crisp texture. The composite bacterial agent of the present invention achieves efficient, targeted fermentation of soy water through complementary functions (acidification, flavor, and degradation), achieving both quality improvement and safety controllability.

[0022] In the present invention, the preparation method of the composite bacterial agent preferably comprises the following steps:

[0023] (1) Lactobacillus plantarum, Lactobacillus acidophilus, Saccharomyces cerevisiae, and Bacillus acidophilus were cultured in liquid until the number of viable cells was ≥1×10 9CFU / mL. The present invention does not particularly limit the propagation method of each strain, and the propagation method commonly used in the field of this technology can be used. As an implementable method, the propagation method of Lactobacillus plantarum CGMCCNo.31144 refers to the information of CN202411131656.7; the propagation method of Lactobacillus acidophilus CICC 6093 and Saccharomyces cerevisiae CICC 1406 refers to the information provided on the official website of the China Industrial Microbiological Culture Collection Administration Center; the propagation method of Bacillus acidophilus CD92-3 refers to the information of "Screening and Identification of High-yield Protease Bacillus in the Fermentation Process of Shanxi Old Vinegar".

[0024] (2) The bacterial solution obtained in step (1) is mixed in proportion and a lyoprotectant is added. The present invention further preferably comprises 15% skim milk powder and 8% trehalose in the lyoprotectant, and more preferably the volume ratio of the lyoprotectant to the bacterial solution is 1:1. As an embodiment, skim milk powder and trehalose are dissolved in sterile physiological saline according to the concentration, mixed with the bacterial solution in a ratio of 1:1 (v / v), and allowed to stand at 25°C for 30 minutes.

[0025] (3) The mixture is freeze-dried to form a powder, vacuum-packed, and stored at 4-10°C. The freeze-drying conditions of the present invention are preferably pre-freezing at -40°C for 2 hours, primary drying at -25°C for 12 hours, and secondary drying at 25°C for 6 hours. More preferably, the mixture is dried to a moisture content of ≤3%. Furthermore, the pulverization is preferably performed using low-temperature airflow pulverization to a powder particle size of 80-100 mesh.

[0026] The present invention provides application of the composite bacterial agent in preparing sauerkraut.

[0027] The present invention also provides a method for preparing sauerkraut by fermenting soy bean water, comprising the following steps:

[0028] (1) Sterilize the soy milk and adjust the pH to 5.0-6.5 and the salt concentration to 2-3%. The soy milk described in the present invention is the waste liquid after the tofu production process after slurrying and forming. As a by-product of tofu production, the soy milk still contains small molecule peptides, free amino acids, oligosaccharides, potassium, magnesium, B vitamins and other ingredients, and has high nutritional value.

[0029] The preferred sterilization temperature of soybean water in the present invention is 80-90°C, more preferably 82-88°C, and more preferably 85°C; the preferred sterilization time is 10-30min, more preferably 15-25min, and more preferably 20min. Preferably, food-grade sodium bicarbonate or citric acid is used to adjust the pH, and it is further preferred to adjust the pH to 6.0. Preferably, food-grade NaCl or water is used to adjust the salt concentration, and it is further preferred that the salt concentration is 2.5%. While high-temperature sterilization is performed, nutrients are retained, and endogenous lipoxygenase and urease in soybean whey are completely inactivated, thereby preventing and controlling the generation of peculiar smell during subsequent fermentation. The initial pH value of soybean water is not suitable for fermentation (gypsum waste liquid is close to neutral, and bittern and GDL waste liquid are acidic). Food-grade sodium bicarbonate or citric acid is used to neutralize it to pH 6.0 to simulate the slightly acidic environment in the initial stage of natural fermentation, promote lactic acid bacteria to start glycolysis, and inhibit the proliferation of spoilage bacteria. In addition to inhibiting Gram-negative bacteria, the appropriate salt concentration also includes salt ions (Na + ) also combines with pectin in vegetable cell walls to maintain the crispness of sauerkraut.

[0030] (2) Inoculate the composite bacterial agent into the soy water and activate the culture for 1-2 hours, more preferably 1.5 hours. The inoculation amount of the composite bacterial agent is preferably 0.1-0.5% of the mass of the soy water, more preferably 0.2-0.4%, and even more preferably 0.3%. The activation culture temperature is preferably 25-30°C, more preferably 28°C.

[0031] In the present invention, glucose is preferably added as an additional carbon source when inoculating the bacterial agent. Further preferably, the amount of glucose added is 0.5-1.5% of the mass of the soy water, more preferably 1%, so as to facilitate fermentation.

[0032] (3) The pre-pickled and dehydrated vegetables are mixed with the soy milk in step (2) and fermented to prepare sauerkraut.

[0033] The present invention preferably pre-salts and dehydrates the vegetables by salting them in an 8-12% NaCl solution at room temperature for 8-12 hours, more preferably in a 10% NaCl solution for 10 hours. Preferably, after salting, the vegetables are maintained at 0.1 MPa for 1 hour to remove free water, and then at 0.3 MPa for 0.5 hour to remove bound water, until the water content of the vegetables reaches 60-65% and the texture is firm. The present invention is not particularly limited to the source of the vegetables, and includes, but is not limited to, leafy vegetables such as Chinese cabbage, mustard greens, and kale.

[0034] The present invention preferably mixes vegetables and soy water in a mass ratio of 1:1-2, more preferably in a mass ratio of 1:1.5, and compacts the vegetables until they are completely submerged. Preferably, fermentation is performed by staged temperature control: fermentation at 20-28°C for 3-5 days, fermentation at 15-20°C for 5-15 days, more preferably fermentation at 25°C for 3-5 days, and fermentation at 18°C for 5-15 days, until the pH is ≤4.2.

[0035] The present invention adopts segmented temperature-controlled fermentation. In the first stage, fermentation at 20-28°C can accelerate the glycolytic metabolism of the bacterial agent, quickly consume soluble sugars such as glucose and sucrose in the soy water, generate lactic acid, and rapidly reduce the pH of the fermentation system from 5.0-6.5 to below 4.5 in 3-5 days, forming a high-acid environment and inhibiting the proliferation of Gram-negative bacteria such as Escherichia coli and Salmonella. The activity of acidophilic Bacillus is enhanced at this temperature, and the secreted protease quickly decomposes soybean globulin in the soy water into small molecular peptides, providing a nitrogen source for lactic acid bacteria. At the same time, the generated soluble sugar can be utilized by brewer's yeast, promoting its proliferation and consuming oxygen in the system, creating an anaerobic environment, and further inhibiting aerobic spoilage bacteria. The high temperature accelerates the acid production of dominant lactic acid bacteria, causing the fermentation environment to enter a low pH in advance during the peak period of nitrite generation, inhibiting the enzyme activity of nitrite-reducing bacteria and reducing nitrite generation. The second stage, at 15-20°C, slows the rate of acid production by lactic acid bacteria and promotes the metabolism of brewer's yeast to produce higher alcohols and esters, giving the sauerkraut its aroma. Lactobacillus acidophilus secretes extracellular polysaccharides (such as glucans and galactans) in a low-acid environment, enhancing the viscoelasticity of the sauerkraut and preventing over-softening. The secreted pectinase continues to act during this stage, specifically degrading the pectin in the intercellular matrix of the vegetables, keeping the vegetables crisp and firm. Low temperatures also inhibit the degradation of small-molecule active ingredients in soy milk water, while slowing the excessive consumption of amino acids by lactic acid bacteria, increasing the free amino acid content and enhancing the umami flavor of the sauerkraut. Staged temperature-controlled fermentation can shorten the fermentation cycle, improve fermentation quality, and reduce energy consumption.

[0036] The present invention also provides a sauerkraut product prepared by the fermentation method.

[0037] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] A composite bacterial agent for preparing sauerkraut by fermenting soy and water, the preparation method is as follows:

[0040] (1) Liquid culture was performed on Lactobacillus plantarum, Lactobacillus acidophilus, Saccharomyces cerevisiae and Bacillus acidophilus respectively until the number of viable cells was ≥1×10 9 CFU / mL;

[0041] (2) mixing the bacterial solution obtained in step (1) in a ratio of 50% of Lactobacillus plantarum, 25% of Lactobacillus acidophilus, 15% of Saccharomyces cerevisiae and 10% of Bacillus acidophilus;

[0042] (3) Dissolve skim milk powder and trehalose in sterile saline (skim milk powder 15% + trehalose 8%), mix with the bacterial solution from step (2) at a ratio of 1:1 (v / v), and let stand at 25°C for 30 min;

[0043] (4) The mixture was freeze-dried to a water content of ≤3%, and then pulverized by low-temperature air flow to form 80-mesh powder, which was vacuum-packed and stored at 4-10°C.

[0044] Example 2

[0045] A composite bacterial agent for preparing sauerkraut by fermenting soy bean water, which differs from Example 1 in that:

[0046] Lactobacillus plantarum 40%, Lactobacillus acidophilus 35%, Saccharomyces cerevisiae 20% and Bacillus acidophilus 5%.

[0047] Example 3

[0048] A composite bacterial agent for preparing sauerkraut by fermenting soy bean water, which differs from Example 1 in that:

[0049] Lactobacillus plantarum 60%, Lactobacillus acidophilus 20%, Saccharomyces cerevisiae 15% and Bacillus acidophilus 5%.

[0050] Example 4

[0051] A method for preparing sauerkraut by fermenting soybeans and water, comprising the following steps:

[0052] (1) Sterilize tofu water (wastewater from tofu production after slurrying and molding) at 85°C for 20 min, adjust the pH to 6.0, and the salt concentration to 2.5%;

[0053] (2) The composite bacterial agent of Example 1 was inoculated into soybean water at an inoculation rate of 0.3%, and activated and cultured at 28°C for 1.5 h;

[0054] (3) Using Chinese cabbage as raw material, pickle it in 10% NaCl solution for 10 h, then squeeze and dehydrate it until the water content of the vegetable is 60%. The vegetable and soy water are mixed in a mass ratio of 1:1.5, and the vegetable is compacted until it is completely immersed;

[0055] (4) Fermentation in a fermenter at 25°C for 4 days and 18°C for 10 days until the pH is ≤ 4.2.

[0056] Example 5

[0057] A method for preparing sauerkraut by fermenting soybeans and water, comprising the following steps:

[0058] (1) Sterilize tofu water (wastewater after slurrying and molding in the tofu production process) at 80°C for 30 min, adjust the pH to 5.0, and the salt concentration to 2%;

[0059] (2) The composite bacterial agent of Example 1 was inoculated into soy water at an inoculation rate of 0.1%, and activated and cultured at 25°C for 2 h;

[0060] (3) Mustard greens were pickled in 8% NaCl solution for 12 h, then squeezed and dehydrated until the water content of the vegetables was 65%. The vegetables were mixed with soy milk and water in a mass ratio of 1:1, and the vegetables were compacted until they were completely immersed;

[0061] (4) Fermentation in a fermenter at 28°C for 3 days and 15°C for 15 days until the pH is ≤ 4.2.

[0062] Example 6

[0063] A method for preparing sauerkraut by fermenting soybeans and water, comprising the following steps:

[0064] (1) Sterilize tofu water (wastewater from tofu production after slurrying and molding) at 90°C for 10 min, adjust the pH to 6.5, and the salt concentration to 3%;

[0065] (2) The composite bacterial agent of Example 1 was inoculated into soybean water at an inoculation rate of 0.5%, and activated and cultured at 30°C for 1 h;

[0066] (3) Cabbage was used as the raw material and pickled in 12% NaCl solution for 8 h. The vegetables were squeezed and dehydrated until the water content of the vegetables was 63%. The vegetables were mixed with soy milk and water in a mass ratio of 1:2 and compacted until the vegetables were completely immersed.

[0067] (4) Fermentation in a fermenter at 20°C for 5 days and 15°C for 12 days until the pH is ≤ 4.2.

[0068] Test Example 1

[0069] 1. Experimental Design

[0070] (1) Materials and equipment:

[0071] Sauerkraut ingredients: fresh Chinese cabbage (variety: Qiuguan), cut into 5×5cm blocks, blanch in boiling water for 2 minutes, then cool and drain.

[0072] Tofu water: taken from a fully automatic tofu production line (pH 5.5, COD 22000 mg / L, total solids 3.8%).

[0073] Traditional saline: 3% NaCl solution (pH 5.5).

[0074] Bacteria: Commercially available Lactobacillus plantarum powder (viable count ≥ 1×10 9 CFU / g).

[0075] Equipment: pH meter, HPLC (high performance liquid chromatography), COD meter, spectrophotometer, constant temperature incubator.

[0076] (2) The experimental groups are shown in Table 1.

[0077] Table 1 Fermentation substrate test groups

[0078]

[0079] Pre-treat soy water: sterilize at 80℃ for 20min, adjust pH to 5.5, salt concentration to 3%.

[0080] (3) Detection indicators and methods:

[0081] Real-time monitoring of pH and nitrite levels was performed on fermentation days 0, 3, 7, 10, and 15. After fermentation, the isoflavone aglycone content, COD removal rate, and nitrite content of the fermented sauerkraut were measured. Ten people blindly sampled the fermented sauerkraut and rated it based on acidity, crispness, and off-flavor.

[0082] The sensory scoring criteria are as follows:

[0083] Acidity: 1-3 points for mild or no sourness, 4-6 points for moderate to acceptable sourness, 7-10 points for distinct and mild sourness without irritation;

[0084] Crispness: 1-3 points for soft or broken fibers, 4-6 points for slightly softened but chewable, 7-10 points for firm and crisp texture with no fiber feeling when chewed.

[0085] Odor: No odor 0 points, slight bitter / musty 1-3 points, obvious odor but acceptable 4-6 points, severe odor unacceptable 7-10 points; bitterness +1 point / level, musty smell +2 points / level, and rotten smell are directly judged as unqualified.

[0086] 2. Test results:

[0087] (1) Acid production rate (pH change)

[0088] As shown in Table 2, when bean water is used as the fermentation matrix for preparing sauerkraut, the acid production rate is significantly faster than that of traditional brine, and the pH is lower after 15 days.

[0089] Table 2 pH changes of sauerkraut prepared with different fermentation matrices

[0090]

[0091] Note: * indicates significant difference between group E and group C (p < 0.05), the same below.

[0092] (2) Functional ingredient retention and safety

[0093] As shown in Table 3, using soy bean water as the fermentation substrate for sauerkraut production preserved isoflavone aglycones and significantly reduced COD, whereas traditional brine had no functional components. Nitrite levels were also significantly lower in the soy bean water group than in the brine group.

[0094] Table 3 Functional components and safety of sauerkraut prepared with different fermentation matrices

[0095]

[0096] (3) Sensory evaluation

[0097] As shown in Table 4, using bean water as the fermentation matrix for preparing sauerkraut has a higher sensory evaluation, no unpleasant odor, and a special bean flavor.

[0098] Table 4 Sensory scores of sauerkraut prepared with different fermentation matrices

[0099] Grouping acidity Crispness Unpleasant smell Bean flavor Group C score (1-10) 7.2±0.8 6.5±1.0 2.5±0.5(bitter) none Group E score (1-10) 8.5±0.6* 7.8±0.7* 0.5±0.2* have

[0100] In summary, using soy water as the fermentation matrix for preparing sauerkraut is superior to traditional brine in terms of acid production rate, functional component retention, safety and sensory evaluation.

[0101] Test Example 2

[0102] Although Experimental Example 1 shows that using soy water as a fermentation matrix for preparing sauerkraut has certain advantages over traditional brine, a single plant lactobacillus cannot fully utilize the components of soy water. Further development of composite bacterial agents and determination of optimal fermentation conditions are needed.

[0103] 1. Experimental Design

[0104] (1) Materials and equipment

[0105] Soybean water: pretreatment was the same as in Experimental Example 1 (pH 5.5, 3% NaCl, sterilization at 80°C for 20 min).

[0106] Bacterial species: Lactobacillus plantarum CGMCC NO.31144; Lactobacillus acidophilus CICC 6093; Saccharomyces cerevisiae CICC 1406; Bacillus acidophilus CD92-3.

[0107] Reagents: glucose (food grade), freeze-dried protective agent (trehalose + skim milk).

[0108] Equipment: constant temperature shaker, gas chromatography-mass spectrometry (GC-MS), fully automatic amino acid analyzer, high-throughput sequencer.

[0109] (2) The experimental groups are shown in Table 5.

[0110] Table 5 Grouping of compound bacterial agent test

[0111]

[0112] Note: The inoculation amount of the microbial agent in all groups is 0.2% of the mass of the soy water, and the number of viable bacteria in the microbial agent is ≥1×10 9 CFU / g.

[0113] (3) Detection indicators and methods

[0114] Protease activity: On the third day of fermentation, the activity was determined by the Folin-phenol method.

[0115] Oligosaccharide retention rate: After fermentation, it was quantitatively determined by LC-MS / MS.

[0116] Ester content: After fermentation, it was determined by GC-MS.

[0117] pH value: pH meter is used to monitor the entire fermentation cycle.

[0118] Energy consumption cost: The electric meter records the power consumption of constant temperature and segmented temperature control throughout the fermentation cycle.

[0119] 2. Test results

[0120] (1) Protease activity and functional components

[0121] As shown in Table 6, the E2 / E3 composite inoculant increased protease activity to over 820 U / g, indicating that the composite inoculant effectively breaks down soy protein in soy water into small peptides. The E2 / E3 group significantly retained oligosaccharides, and supplementation with glucose further promoted yeast ester production.

[0122] Table 6 Functional component conversion efficiency of different fermentation agents and fermentation conditions

[0123]

[0124]

[0125] Note: * indicates that there is a significant difference between group E and group C (p < 0.05), ** indicates that there is an extremely significant difference between group E and group C (p < 0.01), the same below.

[0126] (2) Process optimization effect

[0127] As shown in Table 7, compound bacterial agent + staged temperature control fermentation can significantly shorten the fermentation cycle and save energy, and supplementing carbon source can further shorten the fermentation cycle.

[0128] Table 7 Process effects of different fermentation agents

[0129] index Group C Group E1 Group E2 Group E3 Fermentation cycle 18.5±1.2 16.0±1.0* 12.3±0.8** 10.5±0.5** Energy consumption (kw·h / ton) 85.2±3.5 82.0±3.0 68.5±2.8** 65.3±105**

[0130] Test Example 3

[0131] 1. Experimental Design

[0132] (1) Materials and equipment:

[0133] The sauerkraut of the present invention (Group E) was prepared according to the optimal conditions of Experimental Example 2 (Group E3: composite bacterial agent+staged temperature control+1% glucose).

[0134] Traditional sauerkraut (Group C): naturally fermented in 3% saline for 15 days (same as Group C in Test Example 1).

[0135] Commercially available sauerkraut (Group M): a certain brand of sauerkraut (ingredients: cabbage, water, salt, lactic acid bacteria).

[0136] Main equipment: texture analyzer (TA.XT Plus), amino acid analyzer, pathogenic bacteria detection kit (Salmonella / Staphylococcus aureus).

[0137] (2) Detection indicators and methods:

[0138] The sensory evaluation was the same as that in Test Example 1. The hardness and elasticity of the sauerkraut were determined by texture analysis. The isoflavone aglycone content was determined by HPLC. The retained amount of soybean oligosaccharides was quantitatively determined by LC-MS / MS. The total peptide content was determined by the BCA method. The residual nitrite content was determined according to GB 5009.33. The pathogenic bacteria were detected according to the GB 4789 series.

[0139] 2. Test results

[0140] (1) Sensory scores and texture characteristics

[0141] As shown in Table 8, the pickled beans in group E had a prominent aroma and no unpleasant odor, and their hardness and elasticity were better than those in groups C and M.

[0142] Table 8 Sensory scores and texture characteristics of different sauerkraut

[0143]

[0144]

[0145] Note: * indicates significant difference between group E and group C (p < 0.05)

[0146] (2) Functional ingredients and nutrition

[0147] As shown in Table 9, group E contained isoflavone aglycones and stachyose, and the total peptide content was 4 times that of group C.

[0148] Table 9 Functional components and nutrition of different sauerkraut

[0149] index Group C Group M Group E Isoflavone aglycones (mg / 100g) Not detected Not detected 52.3±3.1 Stachyose retention (mg / g) Not detected Not detected 8.4±0.5 Total peptide content (mg / g) 1.2±0.1 1.5±0.2 4.8±0.3*

[0150] (3) Security

[0151] As shown in Table 10, the nitrite content in Group E was only 40% of that in Group C, and there was no contamination by pathogenic bacteria.

[0152] Table 10 Safety of different sauerkraut

[0153] index Group C Group M Group E Nitrite (mg / kg) 24.3±1.5 18.5±1.2 9.8±0.6* Salmonella detection Positive (1 / 3 samples) Not detected Not detected Staphylococcus aureus detected Positive (1 / 3 samples) Not detected Not detected

[0154] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite bacterial agent for preparing sauerkraut by fermenting soy milk, characterized in that: The bacterial species are comprised in the following mass percentages: 40-60% of Lactobacillus plantarum, 20-35% of Lactobacillus acidophilus, 10-25% of Saccharomyces cerevisiae and 5-15% of Bacillus acidophilus.

2. The composite bacterial agent according to claim 1, characterized in that The preparation method comprises the following steps: (1) Lactobacillus plantarum, Lactobacillus acidophilus, Saccharomyces cerevisiae, and Bacillus acidophilus were cultured in liquid until the number of viable cells was ≥1×10 9 CFU / mL; (2) mixing the bacterial solution obtained in step (1) in proportion and adding a freeze-drying protective agent; (3) The mixture is freeze-dried to form a powder, vacuum-packed and stored at 4-10°C.

3. Use of the composite bacterial agent according to claim 1 or 2 in the preparation of sauerkraut.

4. A method for preparing sauerkraut by fermenting soy milk, characterized in that: The following steps are involved: (1) sterilizing soy milk, adjusting the pH to 5.0-6.5 and the salt concentration to 2-3%; the soy milk is the waste liquid after pulping and forming in the tofu production process; (2) inoculating the composite bacterial agent according to claim 1 or 2 into soy water and activating and culturing for 1-2 hours; (3) The pre-pickled and dehydrated vegetables are mixed with the soy milk in step (2) and fermented to prepare sauerkraut.

5. The fermentation method according to claim 4, characterized in that The temperature of the soy water sterilization is 80-90° C. and the time is 10-30 minutes; and the pH is adjusted using food-grade sodium bicarbonate or citric acid.

6. The fermentation method according to claim 4, characterized in that The inoculation amount of the composite bacterial agent is 0.1-0.5% of the mass of the soy water.

7. The fermentation method according to claim 4, characterized in that The activation culture temperature is 25-30°C.

8. The fermentation method according to claim 4, characterized in that The vegetables are mixed with bean and water in a mass ratio of 1:1-2, and the vegetables are compacted until they are completely immersed.

9. The fermentation method according to claim 4, characterized in that The fermentation is carried out by staged temperature control: fermentation at 20-28° C. for 3-5 days, fermentation at 15-20° C. for 5-15 days, and fermentation until the pH value is ≤4.

2.

10. Sauerkraut produced by the fermentation method according to any one of claims 4 to 9.

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