A low-nitrite-containing fermented solution of anthocyanin-rich Chinese cabbage and a preparation method and application thereof

Abstract

The present application relates to a kind of low nitrite content anthocyanin pickled vegetable fermentation liquor and its preparation method and application, belong to food processing technical field.The method includes: the low salt pickled vegetable fermentation liquor produced by the low salt anaerobic fermentation of the vegetable rich in anthocyanin as raw material is collected, sterilization cooling treatment is carried out, then sterile glucose solution is added, inoculates low salt adaptive bacterial species and carries out secondary anaerobic fermentation, after fermentation is completed, 4 ℃ cold storage 12 h is used to terminate fermentation, using filter membrane filtration, it is obtained.The present application realizes the deep degradation of nitrite in low salt pickled vegetable fermentation liquor by glucose nutrition supplement and secondary pure culture fermentation, while maximumly retaining active ingredients such as anthocyanin, provides safe, high-quality basic raw material for downstream product development, and effectively realizes resource utilization.

Description

Technical Field

[0001] This invention relates to a low-nitrite anthocyanin-containing sauerkraut fermentation broth, its preparation method, and its application, belonging to the field of food processing technology. Background Technology

[0002] In recent years, natural, nutritious, and multifunctional processed foods have become increasingly popular in the market. Among numerous functional ingredients, fruits and vegetables rich in anthocyanins are becoming a research hotspot due to their significant antioxidant and anti-inflammatory activities. Anthocyanins are a class of water-soluble flavonoid natural pigments widely found in plants, which not only give plant tissues rich colors but also have various physiological effects such as scavenging free radicals and inhibiting lipid peroxidation.

[0003] Purple cabbage, purple-red kale, purple-red mustard greens, and purple carrots are edible resources in nature that are rich in anthocyanins and have excellent nutritional value. In terms of processing, besides being eaten fresh, fermentation is one of the important deep-processing technologies for these purple-red vegetables. However, in the traditional vegetable fermentation industry, the core product is almost entirely concentrated on sauerkraut itself, and the large amount of fermentation liquid produced during the fermentation process has always lacked effective development. The fermentation liquid produced by these purple-red vegetables is rich in anthocyanins and probiotic metabolites. Directly discarding it not only wastes the resources of anthocyanin active ingredients and functional small molecules produced by probiotic fermentation, but also increases the cost of wastewater treatment after fermentation, which does not meet the requirements of green and low-carbon production. In-depth analysis revealed several key technical bottlenecks hindering the development and utilization of anthocyanin-rich vegetable fermentation broth: First, controlling nitrite levels under fermentation conditions is challenging. Second, the fermentation broth itself suffers from significant sensory quality defects, with bitterness and off-flavors severely limiting its acceptability for direct consumption or as a food ingredient. Third, anthocyanins and other active substances are easily degraded during subsequent processing, resulting in low retention rates of active ingredients and hindering the high-value utilization of the fermentation broth. Furthermore, existing solutions fail to address the common problem of excessive nitrite levels in low-salt fermentation broths at its source, preventing the realization of an industrial model of "one core fermentation broth, multiple downstream applications," thus limiting further enhancement of the added value of fermentation byproducts. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, this invention provides a low-nitrite, anthocyanin-containing sauerkraut fermentation broth, its preparation method, and its applications. Firstly, this invention utilizes glucose supplementation and secondary pure culture fermentation as core technologies to achieve deep degradation of nitrite in the low-salt sauerkraut fermentation broth, while maximizing the retention of active ingredients such as anthocyanins, providing safe and high-quality raw materials for downstream product development. Secondly, based on the obtained low-nitrite, anthocyanin-containing sauerkraut fermentation broth, functional beverages and flavored sauces are produced, expanding the application scenarios of fermentation byproducts and constructing a resource recycling model of "core raw materials - multiple product categories."

[0005] In a first aspect, the present invention provides a method for preparing a low-nitrite anthocyanin-containing sauerkraut fermentation broth, comprising the following steps: collecting a low-salt sauerkraut fermentation broth produced by low-salt anaerobic fermentation of anthocyanin-rich vegetables, sterilizing and cooling the broth, then adding a sterile glucose solution, inoculating with a low-salt-adapted bacterial strain for secondary anaerobic fermentation, terminating fermentation by refrigerating at 4°C for 12 h after fermentation, and filtering using a filter membrane to obtain a low-nitrite anthocyanin-containing sauerkraut fermentation broth; wherein, the low-salt-adapted bacterial strain in the secondary anaerobic fermentation is inoculated in the form of a bacterial solution, and the viable count of the bacterial solution is 1×10⁻⁶. 7 ~1×10 9 The inoculum concentration was CFU / mL, the inoculum size was 5%~10% (v / v) of the fermentation liquid of low-hydrochloric acid vegetables, the fermentation temperature was 20~25℃, and the fermentation time was 48~72 h.

[0006] In the above technical solution, the anthocyanin-rich vegetables are one or more of the following: purple-red kale, purple cabbage, purple-red mustard greens, purple carrots, purple-red Chinese cabbage, and purple-backed amaranth.

[0007] In the above technical solution, the low-salt anaerobic fermentation conditions are as follows: low-salt adapted bacteria are used for low-salt anaerobic fermentation by spray fermentation or submersion fermentation, the fermentation salt concentration is 0%~2% (w / w), the fermentation temperature is 20~25℃, and the fermentation time is 60~80 days; the low-salt adapted bacteria are inoculated in the form of bacterial liquid, and the viable count of the bacterial liquid is 1×10⁻⁶. 7 ~1×10 9 CFU / mL, inoculum amount is 5%~10% (v / w) of raw material weight.

[0008] Furthermore, salt is added according to the weight of the raw materials during the spraying and fermentation process, without adding any extra water.

[0009] Furthermore, during the immersion fermentation, the mass ratio of raw materials to water is 1:1~3, and salt is added according to the total mass of raw materials and water.

[0010] Furthermore, the low-salt adapted bacterial strain is *Lactobacillus* spp. (Lentilactobacillus) One or more of the low-salt-tolerant lactobacilli.

[0011] Furthermore, the low-salt tolerance refers to the use of a strain with an initial viable count of 1 × 10⁻⁶. 6 When an inoculum of CFU / mL is cultured anaerobically in MRS liquid medium with a NaCl concentration of 0%–2% and a pH of 3.5–5.5 at 30–37°C for 24 h, the viable bacterial count can reach 1 × 10⁻⁶. 8 ~ 1×10 9 CFU / mL.

[0012] Preferably, the low-salt adapted bacterial strain is *Lactobacillus buchneri* (…). Lentilactobacillus buchneri ).

[0013] In the above technical solution, the sterilization and cooling treatment conditions are to treat the low-hydrochloric acid vegetable fermentation liquid at 70~90℃ for 5~20 min and then cool it to 20~22℃.

[0014] In the above technical solution, the mass concentration of the sterile glucose solution is 50%, and the amount added is 1% to 5% (v / v) of the volume of the low-hydrochloric acid vegetable fermentation liquid.

[0015] In the method described in this invention, a glucose solution is added before the secondary anaerobic fermentation to provide a carbon source for the lactic acid bacteria, ensuring their proliferation and metabolic activity, and achieving deep degradation of nitrite (degradation rate ≥50%). At the same time, the anthocyanin retention rate during the secondary fermentation stage is ≥88%. In addition, the glucose addition range provided by this invention can ensure the activity of the strain without affecting the subsequent flavor. If it is too low, it will not meet the nutritional requirements, and if it is too high, it will lead to excessive sweetness.

[0016] In the above technical solution, the filtration conditions are to filter the fermentation broth obtained from the secondary fermentation at 20~25℃ using a microfiltration membrane or an ultrafiltration membrane; wherein, the pore size of the microfiltration membrane is 0.22~0.45 μm, and the molecular rejection rate of the ultrafiltration membrane is 10~100 kDa.

[0017] Furthermore, room temperature membrane separation technology is used to remove impurities while protecting anthocyanins. The anthocyanin retention rate after membrane separation is ≥85%, balancing clarification effect with maintaining anthocyanin retention rate.

[0018] Secondly, the present invention provides a low-nitrite anthocyanin-containing fermented broth of sauerkraut prepared by the above method.

[0019] Furthermore, the nitrite concentration in the low-nitrite anthocyanin-containing sauerkraut fermentation broth is 0.1~0.2 mg / L, and the anthocyanin concentration is 30~45 mg / L.

[0020] Thirdly, the present invention provides the application of the above-mentioned low-nitrite anthocyanin-containing sauerkraut fermentation broth in the preparation of functional beverages or flavored sauces.

[0021] Fourthly, this invention provides a method for preparing functional beverages based on low-nitrite anthocyanin-containing sauerkraut fermentation broth, comprising the following steps: diluting the aforementioned low-nitrite anthocyanin-containing sauerkraut fermentation broth with sterile purified water to a total acid content (calculated as lactic acid) of 5-6.5 g / L and a pH of 4.0-4.5, to obtain a diluted solution; subsequently adding trehalose, ascorbic acid, low-acidity fruit juice, natural sweeteners, and citrus extracts, stirring and mixing evenly, filtering, and sterilizing, to obtain the final product; wherein, based on the volume of the diluted solution, the amount of trehalose added is 0.2%-0.5% (w / v), the amount of ascorbic acid added is 0.05%-0.15% (w / v), and the mass ratio of trehalose to ascorbic acid is 3-4: 1. The amount of low-acidity fruit juice added is 5%~15% (v / v), the amount of natural sweetener added is 0.1%~1% (w / v), and the amount of citrus extract added is 0.05%~0.2% (w / v).

[0022] Furthermore, the low-acidity fruit juice is a fruit juice with a pH value of 3.5~5.0 and a titratable acidity ≤3 g / L (calculated as citric acid).

[0023] Furthermore, the low-acidity fruit juice is one or more of apple juice, pear juice, peach juice, or grape juice.

[0024] Furthermore, the natural sweetener is erythritol.

[0025] Furthermore, the citrus extract is one or more of citrus extract, orange extract, lemon extract, or grapefruit extract.

[0026] Furthermore, the sterilization conditions are: treatment at 20-30°C with ultra-high pressure of 400-600 MPa for 5-10 minutes.

[0027] Fifthly, the present invention provides a method for preparing a flavored sauce based on a low-nitrite anthocyanin-containing sauerkraut fermentation broth, comprising the following steps: adding a natural sweetener, an acidity regulator, and a thickener to the aforementioned low-nitrite anthocyanin-containing sauerkraut fermentation broth, followed by adding one or more of a spice extract, edible flavoring, or preservative, stirring until completely dissolved to obtain a mixed solution; sterilizing to obtain the flavored sauce; wherein, based on the volume of the fermentation broth, the amount of natural sweetener added is 0.05%~0.5% (w / v), the amount of acidity regulator added is 0.1%~0.5% (w / v), the amount of thickener added is 0.1%~0.5% (w / v), the amount of spice extract added is 0.05%~0.3% (w / v), the amount of edible flavoring added is 0.01%~0.1% (v / v), and the amount of preservative added is 0.01%~0.05% (w / v).

[0028] Furthermore, the acidity regulator is citric acid, lactic acid, malic acid, or acetic acid.

[0029] Furthermore, the thickener is xanthan gum, sodium carboxymethyl cellulose, or modified starch.

[0030] Furthermore, the spice extract is capsicum oleoresin.

[0031] Furthermore, the stirring conditions are as follows: stir at 15~25℃ for 5~15 minutes until completely dissolved.

[0032] Furthermore, the sterilization conditions are: treatment at 20-30°C with ultra-high pressure of 400-600 MPa for 5-10 minutes.

[0033] The beneficial effects of this invention are: 1. This invention utilizes a two-stage pure culture fermentation process (with added glucose for nutrient supplementation) to achieve a nitrite degradation rate of ≥50% in the fermentation broth of low-hydrogen saturated vegetables, with a nitrite concentration of 0.1~0.2 mg / L and anthocyanin concentration of 30~45 mg / L. Furthermore, membrane separation removes suspended impurities and off-odor substances, significantly reducing the bitterness sensory score in the fermentation broth. The entire preparation method is mild, minimizing anthocyanin degradation and preserving both functional and nutritional value.

[0034] 2. This invention realizes the high-value reuse of fermentation liquids from various "fermentable anthocyanin-containing purple-red vegetables," constructing a resource recycling model of "multi-raw material adaptation - main product (pickled vegetables) - by-product (fermentation juice)," which can effectively reduce the industrial barriers caused by the limited availability of raw materials in different regions. The low-nitrite fermentation liquid prepared by this invention can be adapted to the development of various products such as functional beverages and flavored sauces, breaking through the limitation of a single utilization path for fermentation by-products; the resulting sauce retains the natural flavor and anthocyanin active ingredients of fermented vegetables, has low nitrite content and good storage stability, and can be used directly as a condiment; the functional beverages obtained after compounding have a harmonious sweet and sour flavor and rich aroma, with an overall acceptance rate 34% higher than that of Comparative Example 3, further enhancing the added value and industrial adaptability of fermentation by-products.

[0035] 3. The raw materials used in this invention are all commonly used in the food industry. The parameters are mild and controllable, and the operating conditions are easy to standardize and control. Both laboratory-scale trials and industrial production are easy to achieve. The production cost is reasonable and it has good development prospects. Attached Figure Description

[0036] Figure 1 This is a graph showing the dynamic changes in nitrite and anthocyanin content during the secondary fermentation of fermentation broth A in Example 1.

[0037] Figure 2 The results show the nitrite and anthocyanin content in the supernatant C of Example 1 and Comparative Example 1.

[0038] Figure 3 The graph shows the trend of nitrite and anthocyanin content in the functional beverage obtained in Example 4 under the condition of storage at 4°C in the dark.

[0039] Figure 4 The graph shows the trend of nitrite and anthocyanin content in the seasoning sauce obtained in Example 7 under the condition of storage at 4°C in the dark. Detailed Implementation

[0040] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0041] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0042] The low-salt adapted strains in the following examples were selected from Lactobacillus buchneri ( Lentilactobacillus buchneri The strain was purchased from the China Industrial Microbial Culture Collection Center (CICC), with strain number CICC20014.

[0043] Example 1 A method for preparing a low-nitrite anthocyanin-containing fermented vegetable broth includes the following steps: Step 1: Raw material screening, pretreatment and primary fermentation (1) Raw material screening and pretreatment Select fresh, unrotten, and pest-free purple-red kale, remove outer old leaves, root impurities, and obviously damaged parts; rinse three times with running water to remove surface dirt and pesticide residues, drain the surface water, and set aside.

[0044] Key raw material indicators: The initial anthocyanin content was 168 mg / 100 g (based on fresh weight).

[0045] (2) Spray-coated low-salt fermentation Pretreated purple-red kale (approximately 5 kg) was placed in a sterile food-grade fermentation tank. Edible salt was added evenly at 1% (w / w, salt / raw material) of the raw material weight, ensuring the salt granules adhered evenly to the surface of the raw material to avoid localized areas of excessively high or low salt concentration. Subsequently, a solution of *Lactobacillus bucherneri* was evenly sprayed onto the kale using a sterilizing spray bottle. The viable count of the solution was 1 × 10⁻⁶. 7 ~1×10 9The inoculation rate is 5% of the raw material weight (v / w, bacterial volume / raw material weight). After spraying, compact the raw material and insert a food-grade pickled cabbage plastic bag (12-mil thickened) of appropriate size into the inside of the fermentation tank. Then, pour a large amount of clean water into the bag until the water level reaches the top of the fermentation tank without overflowing. Use the gravity of the water to squeeze the plastic bag, making it stick tightly to the tank wall and the raw material below, and expelling excess air from the tank, so that the fermentation tank is sealed. Place it in a clean, temperature-controlled room. During fermentation, add water regularly as needed according to the degree of water level drop in the tank.

[0046] Fermentation conditions control: The room temperature is kept constant at 20℃, and the entire anaerobic fermentation process lasts for 70 days to produce low-hydrochloric acid vegetables.

[0047] (3) Fermentation broth collection and stage testing After fermentation, the fermentation tank was removed and the sauerkraut and fermentation liquid were separated. Low-salt sauerkraut fermentation liquid A (about 500 mL) was collected and key indicators were tested. The nitrite content was 0.65 mg / L; the anthocyanin content was 45.01 mg / L; the total acid was 11.0 g / L (calculated as lactic acid); the total bacterial count was ≤1000 CFU / mL, and no pathogenic bacteria were detected.

[0048] Step 2: Secondary anaerobic fermentation for deep degradation of nitrite. (1) Pretreatment of fermentation broth The low-hydrochloric acid vegetable fermentation broth A collected in step 1 was placed in a constant temperature water bath and heated at 80°C for 10 minutes for pasteurization to kill the miscellaneous bacteria in the fermentation broth and prevent them from competing with the secondary fermentation bacteria for nutrients. After sterilization, it was placed at room temperature to cool to 20°C for later use.

[0049] (2) Nutritional supplementation and inoculation Add a 50% sterile glucose solution (w / w) to the cooled fermentation broth A to provide a carbon source for the low-salt-tolerant Lactobacillus bucherneri, ensuring its proliferation and metabolic activity. The amount added is 5% of the volume of fermentation broth A. Subsequently, inoculate 5% of the volume of fermentation broth A with a culture of Lactobacillus bucherneri (viable count 10⁻⁶). 8 (Approximately CFU / mL), inoculate and stir for 10 minutes until completely homogeneous, then seal the fermentation container.

[0050] (3) Secondary fermentation culture and termination control The inoculated fermentation broth was placed in a constant temperature incubator and the fermentation temperature was controlled at 20℃ for anaerobic fermentation for 72 h. During the fermentation process, the nitrite content was measured every 24 h. When the fermentation reached 72 h, the fermentation broth was immediately placed in a 4℃ refrigerator for 12 h to terminate the fermentation and obtain fermentation broth B.

[0051] Fermentation broth B was filtered using a 0.45 μm organic microfiltration membrane. The temperature was controlled at approximately 20℃ during filtration to prevent anthocyanin degradation due to high temperatures. The supernatant C obtained after filtration was collected, which is the low-nitrite, anthocyanin-containing sauerkraut fermentation broth. Key indicators of supernatant C were tested to verify the effects of nitrite reduction and anthocyanin retention. The results showed a nitrite content of 0.195 mg / L, an anthocyanin content of 41.19 mg / L, a nitrite degradation rate of 70%, and an anthocyanin retention rate of 91.51%.

[0052] Example 2 The difference between this embodiment and embodiment 1 is that in step 1 (2), the amount of edible salt added is 0%, and the remaining steps are the same as in embodiment 1.

[0053] Results: After fermentation, the low-hydrochloric acid fermentation broth A was collected, and the nitrite content was measured to be 0.3 mg / L and the anthocyanin content to be 37.64 mg / L. The supernatant C had a nitrite content of 0.11 mg / L and anthocyanin content of 34.22 mg / L, with a nitrite degradation rate of 63.33% and anthocyanin retention rate of 90.91%.

[0054] Example 3 The difference between this embodiment and embodiment 1 is that in step 1 (2), the amount of edible salt added is 2%, and the rest of the steps are the same as in embodiment 1.

[0055] Results: After fermentation, the low-hydrochloric acid fermentation broth A was collected, and the nitrite content was measured to be 0.6 mg / L and the anthocyanin content to be 42.96 mg / L. The supernatant C had a nitrite content of 0.18 mg / L and anthocyanin content of 38.05 mg / L, with a nitrite degradation rate of 70% and an anthocyanin retention rate of 88.57%.

[0056] Example 4 A method for preparing functional beverages based on the low-nitrite, anthocyanin-containing sauerkraut fermentation broth obtained in Example 1 includes the following steps: Step 1: Dilution Adjustment The fermentation broth of low-nitrite anthocyanin-containing sauerkraut (supernatant C) was diluted with sterile purified water. The total acid and pH value were tested during dilution, and the dilution ratio was adjusted to make the total acid of the diluted solution 5.5 g / L (calculated as lactic acid) and pH 4.2, thus obtaining diluted solution D.

[0057] Step 2: Flavor and Nutritional Combination Add the following substances to diluent D in sequence (the addition ratio is based on the volume of diluent D), stirring constantly while adding to ensure thorough mixing: Low-acidity apple juice: pH 4.0, titratable acidity 3 g / L (calculated as citric acid), added at 10% (v / v) to neutralize the sour taste of fermentation liquid and add natural fruit aroma; Erythritol: Added at 0.5% (w / v, g / 100 mL), to adjust sweetness, with no added calories, avoiding the bitter aftertaste of traditional sweeteners; Citrus extract: Added at 1.5% (w / v, g / 100 mL) to enhance the refreshing flavor of the beverage and mask fermentation off-flavors; Trehalose and ascorbic acid: Trehalose was added at 0.3% (w / v, g / 100 mL), and ascorbic acid was added at 0.08% (w / v, g / 100 mL), with a mass ratio of approximately 3.75:1. They synergistically protect anthocyanins, inhibit their degradation, and enhance the antioxidant capacity of the beverage.

[0058] The compounded mixture was filtered through a 150-mesh sterile filter cloth to remove a small amount of undissolved citrus extract particles, resulting in a beverage ready for final adjustment.

[0059] Step 3: Terminal indicator adjustment and ultra-high pressure sterilization After compounding, the beverage was taken out, tested, and its indicators were finely adjusted with sterile purified water to meet the requirements of this invention: the salt concentration was adjusted to 0.45% (within the range of 0.3%-0.5%); the total acid was adjusted to 4.8 g / L (calculated as lactic acid, within the range of 4-6 g / L); finally, about 1000 mL of functional beverage to be sterilized was obtained.

[0060] The beverage to be sterilized is filled into aseptic PET plastic bottles, sealed, and placed in an ultra-high pressure sterilization device. The temperature is controlled at 20℃, the pressure at 500 MPa, and the time at 10 min for ultra-high pressure sterilization. This condition is non-thermal sterilization, which can kill harmful microorganisms while preserving anthocyanins and nutrients to the greatest extent, avoiding nutritional loss and flavor deterioration caused by heat sterilization.

[0061] Results of the final product: The final product contained 0.08 mg / L of nitrite and 20 mg / L of anthocyanins. After 30 days of storage at 4°C, the anthocyanin degradation rate was 8.8%. The final product was stored at 4°C in the dark for 30 days, and samples were taken every 10 days to test the anthocyanin content and calculate the anthocyanin degradation rate. After 30 days of storage, the anthocyanin degradation rate was 8.8%, ≤10%, indicating that the process of this invention can effectively retain anthocyanins and the product has good storage stability.

[0062] Example 5 The difference between this embodiment and embodiment 4 is that the supernatant C used is the supernatant C obtained in embodiment 2, and the remaining steps are the same as in embodiment 4.

[0063] Results: The final product contained 0.08 mg / L of nitrite and 31.13 mg / L of anthocyanins, meeting the core indicator requirements.

[0064] Example 6 The difference between this embodiment and embodiment 4 is that the supernatant C used is the supernatant C obtained in embodiment 3, and the rest of the operations are the same as in embodiment 4.

[0065] Results: The final product contained 0.09 mg / L of nitrite and 9.76 mg / L of anthocyanins. The nitrite degradation effect was comparable to that in Example 4, and the natural functional components of the raw materials were still retained.

[0066] Example 7 A method for preparing sauerkraut-flavored seasoning sauce based on the low-nitrite, anthocyanin-containing sauerkraut fermentation broth obtained in Example 1 includes the following steps: (1) Raw material preparation The supernatant C obtained in Example 1 was tested, and its key indicators are as follows: nitrite content 0.195 mg / L, anthocyanin content 41.19 mg / L, total acid 11.2 g / L (calculated as lactic acid), salt concentration 1%, and total bacterial count ≤100 CFU / mL.

[0067] (2) Preparation and addition of seasonings and condiments Add the following seasonings in the following order (the amount added is based on the volume of the filtrate): Natural sweetener: erythritol, added at 0.2% (w / v, g / 100 mL). Acidity regulator: Citric acid, added at 0.2% (w / v, g / 100 mL). Thickener: Xanthan gum, added at 0.2% (w / v, g / 100 mL). Spices extract: capsicum oleoresin, added at 0.1% (w / v, g / 100 mL).

[0068] The order of addition is as follows: first, pre-dissolve erythritol and citric acid in a small amount of filtrate and add them, stirring for 2 minutes; then, slowly sprinkle xanthan gum onto the liquid surface and stir for 5 minutes until completely dispersed; finally, add chili oil resin and continue stirring for 3 minutes. The temperature should be controlled at 20-25℃ throughout the process.

[0069] (3) Ultra-high pressure sterilization The prepared mixture was filled into sterile PET bottles, sealed, and placed in an ultra-high pressure sterilization device. The sterilization parameters were set as follows: pressure 500 MPa, processing time 10 min, and processing temperature 20℃. After sterilization, the bottles were removed and allowed to cool naturally to room temperature.

[0070] Final product results: The obtained sauerkraut-flavored seasoning sauce is a purplish-red, uniformly viscous liquid with a mild sauerkraut fermentation aroma and a slightly spicy complex flavor. Key indicators tested are as follows: Nitrite content: 0.18 mg / L; Total acid: 11.5 g / L (calculated as lactic acid); pH value: 3.8; Salt concentration: 0.97%; Anthocyanin content: 38.1 mg / L (retention rate ≥92%); Total bacterial count: ≤100 CFU / mL, no pathogenic bacteria detected.

[0071] Comparative Example 1 The difference between this comparative example and Example 1 is that no low-salt-adapted bacteria were inoculated for secondary fermentation; all other operations were the same as in Example 1.

[0072] Comparative Example 2 The difference between this comparative example and Example 1 is that no glucose solution was added, while all other operations were the same as in Example 1.

[0073] Comparative Example 3 The difference between this comparative example and Example 4 is that the supernatant C obtained from Comparative Example 1 was used to prepare the functional beverage, while the rest of the operations were the same as in Example 4.

[0074] Figure 1 This is a graph showing the dynamic changes in nitrite and anthocyanin content during the secondary fermentation process in Example 1. Figure 1 The results showed that the nitrite content continuously decreased during the secondary fermentation process, dropping from an initial 0.65 mg / L to 0.195 mg / L after 72 hours of fermentation. Meanwhile, the anthocyanin content decreased relatively gradually from 45.01 mg / L to 41.19 mg / L, indicating that secondary fermentation effectively reduced the nitrite content while causing minimal damage to anthocyanins.

[0075] Figure 2 The results show the nitrite and anthocyanin content in the supernatant C of Example 1 and Comparative Example 1. Figure 2 It can be seen that, compared with Comparative Example 1 which did not undergo secondary fermentation, Example 1 of the present invention showed a significant advantage in reducing nitrite content. After secondary fermentation, the nitrite content decreased to 0.195 mg / L, significantly lower than that of Comparative Example 1. The anthocyanin content decreased to 41.19 mg / L, with a loss rate of only 8.49% compared to Comparative Example 1.

[0076] Figure 3 The graph shows the changes in nitrite and anthocyanin content of the functional beverage obtained in Example 4 under light-protected storage conditions at 4°C. Figure 3It can be seen that under the storage conditions of 4℃ in the dark, the nitrite content in the fermented beverage remained stable, while the anthocyanin content only decreased slightly. After 30 days, the anthocyanin content was 18.24 mg / L, indicating that the product of this invention has good storage stability.

[0077] Figure 4 The curves showing the changes in nitrite and anthocyanin content in the flavor sauce obtained in Example 7 under light-protected storage conditions at 4°C are presented. Figure 4 It can be seen that under the storage conditions of 4℃ and protected from light, the nitrite content and anthocyanin content in the seasoning sauce remained stable. After 30 days, the anthocyanin content was 36.9 mg / L, indicating that the product of the present invention has good storage stability.

[0078] As shown in Table 1, the degradation effect of nitrite during secondary fermentation is limited without the addition of additional nutrients. However, the degradation rate of nitrite exceeds 50% after the addition of glucose solution.

[0079] Table 1. Nitrite degradation effect after adding glucose during secondary fermentation

[0080] As shown in Tables 2 and 3, the fermented beverage of this invention scores higher than Comparative Example 3 in terms of aroma, sweet and sour balance, and taste. At the same time, the bitterness score is significantly improved, indicating that the secondary fermentation treatment can effectively improve the flavor characteristics of the kale fermentation liquid and significantly enhance the overall acceptability of the product.

[0081] Table 2 Sensory Rating Criteria

[0082] Table 3 Sensory evaluation results

[0083] Table 4 shows that the fermentation broths obtained under different salt concentrations all exhibited significant nitrite degradation during the secondary fermentation process. In Example 5, the nitrite content decreased from 0.30 mg / L to 0.11 mg / L, and in Example 6, it decreased from 0.60 mg / L to 0.18 mg / L, with degradation rates exceeding 50% in both cases. The anthocyanin content of the final product decreased with increasing dilution factor, but remained ≥9 mg / L, retaining its natural functional properties.

[0084] Table 4 Performance test results in Examples 5 and 6

[0085] As shown in Table 5, both products exhibited good stability during storage. pH and total acidity did not change significantly, with fluctuations controlled within 5%, which is within the normal range and will not lead to flavor degradation. The total bacterial count remained ≤100 CFU / mL, with no significant increase observed over 30 days, consistently staying within safe limits.

[0086] Table 5. Changes in indicators of the end products obtained in Examples 4-7 after 30 days of storage.

Claims

1. A method for preparing a low-nitrite anthocyanin-containing fermentation broth from pickled mustard greens, characterized in that: Low-salt sauerkraut fermentation broth, produced from anthocyanin-rich vegetables through low-salt anaerobic fermentation, was collected, sterilized, and cooled. A sterile glucose solution was then added, followed by inoculation with low-salt-adapted microorganisms for secondary anaerobic fermentation. After fermentation, the broth was refrigerated at 4°C for 12 hours to terminate the process. The broth was then filtered through a membrane to obtain a low-nitrite, anthocyanin-containing sauerkraut fermentation broth. The low-salt-adapted microorganisms used in the secondary anaerobic fermentation were inoculated in the form of a bacterial solution with a viable count of 1 × 10⁻⁶. 7 ~1×10 9 The inoculum concentration was CFU / mL, the inoculum size was 5%~10% (v / v) of the fermentation liquid of low-hydrochloric acid vegetables, the fermentation temperature was 20~25℃, and the fermentation time was 48~72 h.

2. The preparation method according to claim 1, characterized in that: The anthocyanin-rich vegetables are one or more of the following: purple-red kale, purple cabbage, purple-red mustard greens, purple carrots, purple-red Chinese cabbage, and purple-backed amaranth.

3. The preparation method according to claim 1, characterized in that: The low-salt anaerobic fermentation conditions are as follows: low-salt adapted bacteria are used for low-salt anaerobic fermentation via spray fermentation or submersion fermentation; the fermentation salt concentration is 0%~2% (w / w); the fermentation temperature is 20~25℃; and the fermentation time is 60~80 days. The low-salt adapted bacteria are inoculated in the form of bacterial solution, and the viable count of the bacterial solution is 1×10⁻⁶. 7 ~1×10 9 CFU / mL, inoculum amount is 5%~10% (v / w) of raw material weight.

4. The preparation method according to claim 1 or 3, characterized in that: The low-salt adapted bacterial strain is *Lactobacillus* genus (…). Lentilactobacillus One or more of the low-salt-tolerant lactobacilli.

5. The preparation method according to claim 1, characterized in that: The sterilization and cooling treatment conditions are as follows: the low-hydrochloric acid vegetable fermentation liquid is treated at 70~90℃ for 5~20 min and then cooled to 20~22℃.

6. The preparation method according to claim 1, characterized in that: The sterile glucose solution has a mass concentration of 50% and is added at a rate of 1% to 5% (v / v) of the volume of the low-hydrochloric acid vegetable fermentation liquid.

7. The low-nitrite anthocyanin-containing sauerkraut fermentation broth prepared by the method according to any one of claims 1 to 6, characterized in that: The nitrite concentration in the fermentation broth of the low-nitrite anthocyanin-containing sauerkraut is 0.1~0.2 mg / L, and the anthocyanin concentration is 30~45 mg / L.

8. The application of the low-nitrite anthocyanin-containing sauerkraut fermentation broth according to claim 7 in the preparation of functional beverages or flavored sauces.

9. A method for preparing functional beverages based on fermented broth of low-nitrite anthocyanin-containing sauerkraut, characterized in that: The low-nitrite anthocyanin-containing sauerkraut fermentation broth of claim 7 is diluted with sterile purified water to a total acid content of 5-6.5 g / L (calculated as lactic acid) and a pH of 4.0-4.5 to obtain a diluted solution. Then, trehalose, ascorbic acid, low-acidity fruit juice, natural sweetener, and citrus extract are added, stirred and mixed evenly, filtered, and sterilized to obtain the final product. Specifically, based on the volume of the diluted solution, the amount of trehalose added is 0.2%-0.5% (w / v), the amount of ascorbic acid added is 0.05%-0.15% (w / v), the mass ratio of trehalose to ascorbic acid is 3-4:1, the amount of low-acidity fruit juice added is 5%-15% (v / v), the amount of natural sweetener added is 0.1%-1% (w / v), and the amount of citrus extract added is 0.05%-0.2% (w / v).

10. A method for preparing flavored seasoning sauce based on fermentation broth of low-nitrite anthocyanin-containing sauerkraut, characterized in that: Add a natural sweetener, an acidity regulator, and a thickener to the low-nitrite anthocyanin-containing sauerkraut fermentation liquid as described in claim 7, followed by the addition of one or more of spice extracts, edible flavorings, or preservatives, and stir until completely dissolved to obtain a mixed solution; sterilize to obtain a flavored sauce; wherein, based on the volume of the fermentation liquid, the amount of natural sweetener added is 0.05%~0.5% (w / v), the amount of acidity regulator added is 0.1%~0.5% (w / v), the amount of thickener added is 0.1%~0.5% (w / v), the amount of spice extract added is 0.05%~0.3% (w / v), the amount of edible flavoring added is 0.01%~0.1% (v / v), and the amount of preservative added is 0.01%~0.05% (w / v).

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