Microbial fermentation-based hotpot condiment and preparation method thereof

Abstract

This invention discloses a hot pot base based on microbial fermentation and its preparation method, belonging to the field of food fermentation technology. The method includes: S1, crushing broad beans and inoculating them with Aspergillus oryzae to produce koji, obtaining broad bean koji material; melting butter and adding an anti-caking agent; S2, mixing the broad bean koji material with auxiliary materials, then sequentially inoculating with lactic acid bacteria and yeast starter, performing segmented temperature and humidity controlled fermentation with intermittent ventilation to obtain a fermentation base; S3, terminating fermentation when volatile flavor substances reach a preset threshold; S4, adding salt and / or sugar to the fermentation base for acidity control; S5, sequentially performing low-temperature vacuum concentration, filling and sealing, and sterilization to obtain the finished product. This invention, through multi-strain relay fermentation and acidity control, significantly shortens the fermentation cycle, increases the content of flavor substances and batch stability, improves the product's color and taste, and achieves rapid, safe, and standardized industrial production of hot pot base.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a hot pot base based on microbial fermentation and its preparation method. Background Technology

[0002] Currently, the mainstream hot pot base preparation process mostly adopts a high-temperature frying combined with the natural fermentation of broad bean paste. This process requires the raw materials to undergo long-term cellar aging and maturation treatment, with a conventional maturation cycle of 6 months or more. It is the mainstream traditional process for the industrial production of hot pot base.

[0003] However, practical application and research have verified that this traditional natural fermentation preparation process has inherent technical defects, which seriously restrict the quality of hot pot base products and the large-scale development of the industry. The specific technical defects are as follows:

[0004] First, the product's flavor stability is poor, and batch consistency is difficult to guarantee. Traditional processes rely on the natural environment to complete the fermentation process, and the fermentation effect is highly dependent on external temperature and humidity conditions. The microbial community structure within the fermentation system is complex and its activity is unstable, making it extremely susceptible to environmental fluctuations. This results in significant differences in the composition and content of flavor substances between different batches of hot pot base. Existing research data supports this, showing that the difference in volatile flavor substances between different batches of hot pot base prepared using traditional processes can exceed 40% (Food Science, 2020). This makes it impossible to achieve standardized and controllable production of product flavor, resulting in a significant deficiency in product quality consistency.

[0005] Secondly, the product poses significant food safety risks and has poor market adaptability. The traditional open-air natural fermentation and cellar aging environment, which lasts for months, makes it impossible to precisely control the growth of miscellaneous bacteria, easily leading to the proliferation of toxin-producing molds and other harmful microorganisms, causing contamination of the base material. To inhibit bacterial spoilage and extend product shelf life, manufacturers typically need to add excessive amounts of preservatives, such as sodium benzoate at up to 0.5g / kg. This not only fails to meet the development needs of improving the quality and efficiency of food safety production but also increases the product's food safety risks, reduces consumer acceptance, and hinders market promotion.

[0006] Third, the production cycle is long, production efficiency is low, and production costs are high. Traditional processes require a aging period of more than 6 months in cellars, and the entire production process occupies a large amount of storage space for raw materials and semi-finished products. This significantly ties up the company's storage resources and working capital, resulting in low capital turnover efficiency and high overall production costs, approximately 15-20 yuan / kg. This technological shortcoming greatly limits the batch, large-scale industrial production of hot pot base products, hindering the industry's industrialization and standardization upgrade.

[0007] In summary, the existing traditional natural fermentation process for hot pot base has many technical drawbacks, such as uncontrollable flavor, poor quality consistency, high food safety risks, low production efficiency, and high production costs. The industry urgently needs to develop a new fermentation process for hot pot base that can achieve controllable flavor, safety and efficiency, stable quality, and is suitable for industrial-scale production. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a hot pot base based on microbial fermentation and its preparation method, which solves the problems of uncontrollable flavor, poor quality consistency, high food safety risk, low production efficiency and high production cost of the existing technology.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing hot pot base based on microbial fermentation includes the following steps:

[0011] S1. Raw material pretreatment: Crush broad beans to a particle size ≤1.5mm, inoculate with Aspergillus oryzae for koji fermentation to obtain broad bean koji material; melt butter in a 70-85℃ water bath and mix with an anti-caking agent;

[0012] S2. Multi-strain relay fermentation: After mixing broad bean koji, butter and auxiliary materials such as chili and spices, lactic acid bacteria starter and yeast starter are inoculated in sequence, and staged temperature and humidity control and intermittent ventilation fermentation are carried out to obtain fermentation base material.

[0013] S3. Fermentation endpoint determination: When the volatile flavor substances in the fermentation system reach a preset threshold, the fermentation is terminated.

[0014] S4. Post-processing: The material after fermentation is terminated is concentrated under low temperature and vacuum, then filled into packaging containers and sealed. The sealed packaging is then sterilized to obtain the finished hot pot base.

[0015] Preferably, the Aspergillus oryzae used for fermentation in step S1 is Aspergillus oryzae Hu Niang 3.042; the lactic acid bacteria starter in step S2 includes Lactobacillus plantarum and Lactobacillus brevis, wherein Lactobacillus plantarum is strain CICC 6240 and Lactobacillus brevis is strain CICC 6239, with a live bacteria ratio of 2:1 to 4:1; the yeast starter includes Saccharomyces rouxii.

[0016] Preferably, the segmented temperature and humidity control and intermittent ventilation fermentation includes:

[0017] Lactic acid bacteria fermentation stage: control the temperature at 30-32℃, the relative humidity at 75-85%, and anaerobic fermentation for 24-30 hours;

[0018] Yeast relay fermentation stage: After adding yeast starter, control the temperature at 28-32℃ and the relative humidity at 70-80%. Use intermittent ventilation fermentation, ventilating and stirring every 6-8 hours. After each ventilation and stirring, let it stand for anaerobic fermentation for 6-8 hours. Alternate between aerobic and anaerobic fermentation. The total fermentation time is 48-72 hours.

[0019] Preferably, after determining the fermentation endpoint in step S3 and before the post-treatment in step S4, an acidity control step is further included:

[0020] Salt and / or sugar are added to the fermentation substrate to balance the acidity, so that the total acidity of the fermentation substrate is controlled at 0.8-1.5g / 100g and the salinity is controlled at 8-12%; the amount of salt added is 6-10% of the mass of the fermentation substrate and the amount of sugar added is 1-3% of the mass of the fermentation substrate.

[0021] Preferably, the fermentation endpoint is determined by using an electronic nose to detect the content of volatile compounds in the fermentation product, and simultaneously detecting the acid value and peroxide value. Fermentation is terminated when esters ≥12mg / kg, alcohols ≥8mg / kg, acid value ≤5mg / g, and peroxide value ≤0.25g / 100g. The detection results of the electronic nose are pre-calibrated using a gas chromatography-mass spectrometry system.

[0022] Preferably, the fermentation process is monitored and regulated by a fermentation control system, which includes:

[0023] The sensor group, which includes a temperature sensor, an online pH detection module, and an ORP sensor, is used to collect temperature, pH value, and redox potential signals inside the fermenter.

[0024] A programmable logic controller (PLC) is connected to the sensor group and each execution module, respectively, and is used to receive feedback signals from the sensor group, compare and calculate with a preset fermentation curve, and output control commands.

[0025] The execution module includes a heating device, a humidifying device, and a ventilation device, which adjust the temperature, humidity, and ventilation volume inside the fermenter according to the control instructions output by the programmable logic controller;

[0026] The human-machine interface is bidirectionally connected to the programmable logic controller and is used to display data, modify fermentation parameters, and provide alarm prompts.

[0027] The electronic nose detection unit is activated when the fermentation endpoint is determined. It is used to detect the content of volatile flavor substances and feed the result back to the programmable logic controller. The programmable logic controller then decides whether to terminate the fermentation based on a preset threshold.

[0028] Preferably, the sterilization is ultra-high pressure sterilization, with the following conditions: pressure 550-650 MPa, time 8-12 minutes. Pulsed electric field sterilization or low-temperature plasma sterilization can also be used.

[0029] Preferably, the conditions for the low-temperature vacuum concentration are: temperature 45-55℃, vacuum degree -0.07 to -0.09MPa.

[0030] Preferably, the anti-caking agent is silicon dioxide, and the amount added is 0.05%-0.2% of the weight of the tallow.

[0031] A hot pot base based on microbial fermentation is prepared using the method described above.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention constructs a complete flavor formation chain through Aspergillus oryzae koji making, relay fermentation by lactic acid bacteria and yeast, and alternating aerobic / anaerobic processes. This chain consists of "Aspergillus oryzae producing enzymes to degrade macromolecules and provide precursor substances → lactic acid bacteria producing acid to inhibit bacteria → yeast producing alcohols and esters to generate aroma," simulating the multi-strain synergistic fermentation environment of traditional fermented soybean paste, characterized by sun exposure and night dew. The synergistic effect of the three strains results in a total flavor content of 390-420 mg / kg, which is 4.2-4.6 times that of traditional natural fermentation (92 mg / kg). The number of volatile flavor compounds reaches 92-96 (compared to only 52 in traditional processes). Simultaneously, the large amount of amino acids and reducing sugars produced by Aspergillus oryzae koji making accelerates the Maillard reaction and enzymatic browning during the aerobic fermentation stage, giving the product a natural reddish-brown color. This overcomes the shortcomings of single lactic acid bacteria fermentation, which results in a thin flavor and insufficient color.

[0034] 2. This invention utilizes the relay fermentation of lactic acid bacteria and yeast to form a dominant microbial community (accounting for >80%), effectively inhibiting the growth of other microorganisms. The total number of other microorganisms can be controlled at an extremely low level of ≤10² CFU / g (compared to >10 in traditional processes). 4 (CFU / g) eliminates the need for added chemical preservatives such as sodium benzoate. Furthermore, a post-fermentation acidity control step is implemented, precisely balancing organic acids with salt and sugar to maintain the total acidity within a palatable range of 0.8-1.5g / 100g, resolving the overly acidic taste defect often associated with single-lactic acid bacteria fermentation. Combined with the precise control of the fermentation system, the batch-to-batch variation coefficient (CV) is reduced from >20% in traditional processes to ≤3%, achieving standardization and consistency in product quality.

[0035] 3. This invention shortens the traditional natural fermentation cycle of more than 6 months to 66-72 hours, increases production efficiency by more than 90%, and significantly reduces storage costs; it adopts low-temperature vacuum concentration combined with ultra-high pressure sterilization technology, and the retention rate of compound aroma substances is ≥91%, avoiding the burnt taste and flavor loss caused by traditional high-temperature sterilization, and realizing the rapid, safe and standardized industrial production of hot pot base. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the fermentation control system in this invention. Detailed Implementation

[0037] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] Please see Figure 1 This embodiment provides a method for preparing hot pot base based on microbial fermentation, and the specific steps are as follows:

[0041] S1, Raw material pretreatment

[0042] Select high-quality broad beans and crush them to an average particle size of 1.2mm using a hammer crusher.

[0043] Fermentation and koji making: Moisten the crushed broad beans to a moisture content of 40-45%, sterilize by high-pressure steaming (121℃, 15 minutes), and cool to 35-40℃. Inoculate with Aspergillus oryzae (Hu Niang 3.042 koji essence) at 0.3-0.5% of the broad bean weight, stir evenly, and place in a koji tray. Control the temperature at 30-35℃ and the relative humidity at 90-95% and cultivate for 48-60 hours until the surface of the broad beans is covered with yellow-green spores. This is the broad bean koji material.

[0044] Weigh 100 kg of butter and place it in a jacketed heating carburetor. Heat it in an 80°C water bath until completely melted. Then add 0.1 kg of food-grade silica powder (0.1% of the weight of the butter), stir well, and set aside.

[0045] S2, Multi-strain Relay Fermentation

[0046] Strain activation: Lyophilized Lactobacillus plantarum (a known commercial strain, available through commercial channels such as the China Industrial Microbial Culture Collection Center (CICC), e.g., CICC 6240 strain) and Lactobacillus brevis (also available through CICC) were rehydrated and activated separately with sterile physiological saline. The bacterial concentration was then counted and adjusted to 10⁻⁶. 8 CFU / mL. In this embodiment, *Lactobacillus plantarum* and *Lactobacillus brevis* are both commercially known strains in the art, which can be directly purchased by the public through commercial channels such as the China Industrial Microbiological Culture Collection Center (CICC, Building 6, No. 24, Jiuxianqiao Middle Road, Chaoyang District, Beijing) before the application date. Those skilled in the art can obtain the specific strains required to implement this invention based on the scientific names and purchase channels described in this specification, without the need for additional biological material preservation.

[0047] Lactic acid bacteria fermentation: Mix broad bean koji, melted butter, 50kg of Pixian broad bean paste (low-salt version, salinity ≤10%), 30kg of fermented chili paste, 5kg of Sichuan peppercorns, and 2kg of spice packet to form the fermentation substrate. At a live bacteria ratio of 3:1, take 7.1L of *Lactobacillus plantarum* inoculum and 2.4L of *Lactobacillus brevis* inoculum (total approximately 9.5L), mix them, and spray evenly onto the fermentation substrate. The total inoculum amount is approximately 5% of the total mass of the fermentation substrate. Control the temperature at 30-32℃ and the relative humidity at 80%, and anaerobic ferment for 24 hours.

[0048] Yeast relay fermentation: After the lactic acid bacteria fermentation is completed, Saccharomyces rouxii culture is inoculated at a rate of 2% of the total mass of the fermentation substrate (approximately 3.8 L, culture concentration 10). 7 (CFU / mL). Intermittent aerated fermentation was adopted: the temperature was controlled at 28-32℃ and the relative humidity at 75%. The aeration and stirring device was turned on every 6 hours for 30 minutes of aerobic fermentation, followed by 6 hours of static anaerobic fermentation. The aerobic and anaerobic processes were alternated, with a total fermentation time of 60 hours.

[0049] The fermentation control system includes:

[0050] Sensor group: Includes temperature sensor, pH online detection module and ORP sensor (oxidation-reduction potential sensor), used to collect temperature, pH value and ORP value signals in fermenter;

[0051] Programmable Logic Controller (PLC): Connected to the sensor group and each execution module respectively, used to receive feedback signals from the sensor group, compare and calculate with the preset fermentation curve, and output control commands;

[0052] Execution module: Includes heating device, humidification device and ventilation device, which adjusts the temperature, humidity and ventilation in the fermenter according to the control instructions output by PLC;

[0053] Human-Machine Interface (HMI): Connects bidirectionally to the PLC for displaying data, modifying fermentation parameters, and providing alarm prompts;

[0054] Electronic nose detection unit: used to detect the content of volatile flavor compounds when determining the fermentation endpoint.

[0055] S3, Determination of Fermentation Endpoint

[0056] At the end of fermentation, the electronic nose detection unit connected to the fermenter was activated for detection. This electronic nose had been pre-calibrated using GC-MS (Gas Chromatography-Mass Spectrometry), and standard curves (R² > 0.99) were established between the ester and alcohol contents and the sensor response signal. Details are as follows:

[0057] Different concentrations of ester and alcohol standards were taken and their contents were determined by GC-MS. Simultaneously, an electronic nose was used to detect the response signal, and a standard curve was fitted using the least squares method. After detecting the content of volatile flavor compounds, the electronic nose fed back the results to the PLC controller.

[0058] Simultaneously, samples were taken and tested for acid value and peroxide value according to GB 5009.229-2016 and GB 5009.227-2016 methods.

[0059] When the test results show that the content of esters is 14 mg / kg, the content of alcohols is 9 mg / kg, the acid value is 4.2 mg / g, and the peroxide value is 0.18 g / 100g, the fermentation is considered complete and the fermentation is stopped.

[0060] After determining the fermentation endpoint, add salt and / or sugar to the fermentation substrate to balance the acidity. The specific steps are as follows:

[0061] The total acid content (calculated as lactic acid) of the fermentation substrate was tested according to the method in GB12456-2021 "National Food Safety Standard - Determination of Total Acid in Food". Based on the test results, 6-10% salt and 1-3% sugar by weight were added to the fermentation substrate and stirred evenly to control the total acid (calculated as lactic acid) at 0.8-1.5g / 100g, the salinity at 8-12%, and the taste to be a harmonious balance of sweet, sour, salty and umami.

[0062] In this step, salt is used to inhibit the growth of residual bacteria and enhance the savory flavor, while sugar is used to neutralize the organic acids produced by lactic acid bacteria fermentation and to soften the taste. The two work synergistically to avoid the problem of excessive sourness caused by fermentation with only lactic acid bacteria, resulting in a more harmonious flavor in the final product.

[0063] S4, Post-processing

[0064] Low-temperature vacuum concentration: The fermented material is pumped into a low-temperature vacuum concentration device, and the internal temperature of the device is controlled at 50℃ and the vacuum degree is -0.08MPa. The material is concentrated to 80% of its original volume to obtain concentrated fermentation base material.

[0065] Filling and sealing: The above-mentioned concentrated fermentation base material is quantitatively filled into flexible packaging bags and then vacuum sealed.

[0066] Sterilization: Place the sealed bag of product into the processing chamber of an ultra-high pressure equipment and maintain the pressure at 600MPa for 10 minutes at room temperature to obtain the finished hot pot base.

[0067] It should be noted that before inoculation, the activated bacterial solution can be concentrated by low-temperature centrifugation (4000 rpm, 15 min), then resuspended in a small amount of sterile physiological saline, and then sprayed evenly for inoculation. This is to control the amount of external water introduced and avoid the fermentation system's water activity (Aw) being too high, which would affect the fermentation stability.

[0068] Example 2

[0069] This embodiment is basically the same as embodiment 1, except that:

[0070] S1, Raw material pretreatment

[0071] Select high-quality broad beans and crush them to an average particle size of 1.2mm using a hammer crusher. Moisten the crushed broad beans to a moisture content of 40-45%, sterilize them by high-pressure steaming (121℃, 15 minutes), and then cool them to 35-40℃. Inoculate 0.4% of the broad bean weight with Aspergillus oryzae 3.042 koji, stir well, and place in a koji tray. Control the temperature at 32℃ and the relative humidity at 92%, and incubate for 52 hours until the surface of the broad beans is covered with yellow-green spores. This yields the broad bean koji.

[0072] Weigh 100 kg of butter and place it in a jacketed heating carburetor. Heat it in an 80°C water bath until completely melted. Then add 0.1 kg of food-grade silica powder (0.1% of the weight of the butter), stir well, and set aside.

[0073] Take 50kg of Pixian broad bean paste (low-salt version, salt content ≤10%), 30kg of fermented chili paste, 5kg of Sichuan peppercorns, and 2kg of spice packet (star anise, cinnamon, fennel, etc.), mix them with the above-mentioned broad bean starter and melted butter to form a fermentation substrate.

[0074] S2, Multi-strain Relay Fermentation

[0075] Microbial activation: Lyophilized Lactobacillus plantarum (CICC 6240) and Lactobacillus brevis (CICC 6239) were rehydrated and activated separately with sterile physiological saline. The bacterial counts were then performed and the bacterial concentration was adjusted to 10⁻⁶. 8 CFU / mL. The lyophilized Saccharomyces rouxii powder was rehydrated and activated with sterile malt extract medium, and the bacterial concentration was adjusted to 10. 7 CFU / mL.

[0076] Lactic acid bacteria fermentation: Mix *Lactobacillus plantarum* and *Lactobacillus brevis* bacterial cultures at a live bacteria ratio of 2:1 (total inoculum amount is 5% of the fermentation substrate mass), and spray evenly onto the fermentation substrate. Control the temperature at 31℃ and the relative humidity at 80%, and perform anaerobic fermentation for 21 hours.

[0077] Yeast relay fermentation: After the lactic acid bacteria fermentation is completed, *Saccharomyces rouxii* liquid is inoculated (the inoculum amount is 2% of the fermentation substrate mass). Intermittent aerated fermentation is adopted: the temperature is controlled at 30℃ and the relative humidity at 75%. The aeration and stirring device is turned on every 8 hours for 30 minutes of aerobic fermentation, followed by static anaerobic fermentation. The aerobic and anaerobic processes are alternated, with a total fermentation time of 50 hours.

[0078] The structure of the fermentation control system is the same as that in Example 1, and will not be described again here.

[0079] S3, Determination of Fermentation Endpoint

[0080] Following the same method as in Example 1, an electronic nose was used to detect the content of volatile flavor compounds, along with the acid value and peroxide value. Fermentation was deemed complete and stopped when the test results showed: ester content 12.5 mg / kg, alcohol content 8.2 mg / kg, acid value 4.5 mg / g, and peroxide value 0.20 g / 100g.

[0081] acidity control

[0082] According to GB 12456-2021, the total acid content of the fermentation substrate was tested. Salt (7% of the mass of the fermentation substrate) and sugar (1.5% of the mass of the fermentation substrate) were added to the fermentation substrate and stirred evenly to control the total acid (calculated as lactic acid) at 1.0-1.2g / 100g and the salinity at 9-10%.

[0083] S4, Post-processing

[0084] The low-temperature vacuum concentration conditions are 45℃ and vacuum degree -0.07MPa; after concentration, it is filled and sealed, and then treated under ultra-high pressure at 550MPa for 12 minutes to obtain the finished hot pot base.

[0085] Example 3

[0086] This embodiment is basically the same as embodiment 1, except that:

[0087] S1, Raw material pretreatment

[0088] Select high-quality broad beans and crush them to an average particle size of 1.2mm using a hammer crusher. Moisten the crushed broad beans to a moisture content of 40-45%, sterilize them by high-pressure steaming (121℃, 15 minutes), and then cool them to 35-40℃. Inoculate 0.5% of the broad bean weight with Aspergillus oryzae 3.042 koji, stir well, and place in a koji tray. Control the temperature at 35℃ and the relative humidity at 95% for 60 hours, until the surface of the broad beans is covered with yellow-green spores; this yields the broad bean koji.

[0089] Weigh 100 kg of butter and place it in a jacketed heating carburetor. Heat it in an 80°C water bath until completely melted. Then add 0.1 kg of food-grade silica powder (0.1% of the weight of the butter), stir well, and set aside.

[0090] Take 50kg of Pixian broad bean paste (low-salt version, salt content ≤10%), 30kg of fermented chili paste, 5kg of Sichuan peppercorns, and 2kg of spice packet (star anise, cinnamon, fennel, etc.), mix them with the above-mentioned broad bean starter and melted butter to form a fermentation substrate.

[0091] S2, Multi-strain Relay Fermentation

[0092] Microbial activation: Lyophilized Lactobacillus plantarum (CICC 6240) and Lactobacillus brevis (CICC 6239) were rehydrated and activated separately with sterile physiological saline. The bacterial counts were then performed and the bacterial concentration was adjusted to 10⁻⁶. 8 CFU / mL. The lyophilized Saccharomyces rouxii powder was rehydrated and activated with sterile malt extract medium, and the bacterial concentration was adjusted to 10. 7 CFU / mL.

[0093] Lactic acid bacteria fermentation: Mix *Lactobacillus plantarum* and *Lactobacillus brevis* bacterial cultures at a live bacteria ratio of 4:1 (total inoculum amount is 5% of the fermentation substrate mass) and spray evenly onto the fermentation substrate. Control the temperature at 32℃ and the relative humidity at 75%, and perform anaerobic fermentation for 26 hours.

[0094] Yeast relay fermentation: After the lactic acid bacteria fermentation is completed, *Saccharomyces rouxii* broth is inoculated (the inoculum amount is 2% of the fermentation substrate mass). Intermittent aerated fermentation is adopted: the temperature is controlled at 28℃ and the relative humidity at 72%. The aeration and stirring device is turned on every 6 hours for 30 minutes of aerobic fermentation, followed by static anaerobic fermentation. The aerobic and anaerobic processes are alternated, with a total fermentation time of 48 hours.

[0095] The structure of the fermentation control system is the same as that in Example 1, and will not be described again here.

[0096] S3, Determination of Fermentation Endpoint

[0097] Following the same method as in Example 1, an electronic nose was used to detect the content of volatile flavor compounds, along with the acid value and peroxide value. Fermentation was deemed complete and stopped when the test results showed: ester content 13.8 mg / kg, alcohol content 8.5 mg / kg, acid value 4.0 mg / g, and peroxide value 0.16 g / 100g.

[0098] acidity control

[0099] According to GB 12456-2021, the total acid content of the fermentation substrate was tested. Salt (9% of the mass of the fermentation substrate) and sugar (2.5% of the mass of the fermentation substrate) were added to the fermentation substrate and stirred evenly to control the total acid (calculated as lactic acid) at 0.9-1.1g / 100g and the salinity at 10-12%.

[0100] S4, Post-processing

[0101] The low-temperature vacuum concentration conditions are 55℃ and a vacuum degree of -0.09MPa; after concentration, it is filled and sealed, and then treated under ultra-high pressure at 650MPa for 8 minutes to obtain the finished hot pot base.

[0102] Example 4 (Simplified Process)

[0103] This embodiment is basically the same as embodiment 1, except that:

[0104] The starter culture uses only Lactobacillus plantarum (single strain) and does not contain Lactobacillus brevis.

[0105] The fermentation endpoint is determined solely by the electronic nose to detect volatile substances, without detecting acid value and peroxide value (but the final product still meets national standards).

[0106] The sterilization process in post-treatment was changed to pasteurization (62℃, 30 minutes).

[0107] The structure of the fermentation control system is the same as that in Example 1, and will not be described again here.

[0108] This embodiment is used to demonstrate a simplified implementation of the technical solution of the present invention. Although the content of flavor substances and batch stability are slightly lower than those in Examples 1-3, they are still significantly better than the traditional process.

[0109] Comparative Example 1 (Traditional Process)

[0110] The process employs a traditional high-temperature roasting + natural fermentation method: Raw materials (excluding silica) in the same proportion are roasted at high temperature (160-180℃) for an extended period (approximately 2 hours), then placed in ceramic jars and naturally aged and fermented in a room-temperature warehouse away from light for 6 months. After fermentation, the material is removed and sterilized at 95℃ for 30 minutes, then cooled and bottled.

[0111] Comparative Example 2 (single strain, non-segmented fermentation)

[0112] A single Lactobacillus plantarum starter culture was used (the number of live bacteria was the same as the total number of live bacteria in Example 1), without segmented temperature and humidity controlled fermentation (constant temperature of 32°C and constant humidity of 70% for 72 hours throughout the process), and the remaining steps were the same as in Example 1.

[0113] Performance testing and effect comparison

[0114] Key performance indicators of the hot pot bases prepared in Examples 1-4 and Comparative Examples 1-2 were tested, and the results are shown in the table below:

[0115] index Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Total fermentation cycle 72 hours 71 hours 66 hours 72 hours 6 months 72 hours Total flavor compounds (mg / kg) 420 390 405 210 92 145 Number of volatile substances 96 92 94 62 52 58 viable lactic acid bacteria count (log CFU / g) 8.2 8.0 8.1 8.5 6.5 7.8 Yeast percentage (%) 25 28 22 0 10 0 Total acid (after adjustment, calculated as lactic acid, g / 100g) 1.2 1.1 1.0 2.5 (Unregulated) 0.8 2.0 (Unregulated) Batch-to-batch variation (CV%) 2.8 3.0 2.9 5.2 23.5 12.6 Total bacterial count (CFU / g) ≤10² ≤10² ≤10² ≤10³ <![CDATA[>10 4 ]]> Approximately 10³ Sodium benzoate dosage (g / kg) 0 0 0 0 0.5 0.2 Flavor retention rate (%) 93 91 92 85 58 91

[0116] The following conclusions can be drawn from the above test results:

[0117] 1. Examples 1-3 of this invention (preferred schemes): Through Aspergillus oryzae koji preparation, relay fermentation of lactic acid bacteria and yeast, and alternating aerobic / anaerobic processes, multi-strain synergistic fermentation is achieved. The fermentation cycle is only 66-72 hours, and the total content of flavor substances is as high as 390-420 mg / kg, which is 4.2-4.6 times that of the traditional process (92 mg / kg). The number of volatile flavor substances reaches 92-96, which is more than 80% higher than that of the traditional process (52 types). The proportion of yeast reaches 22-28%, demonstrating the advantages of multi-strain fermentation. After acidity control, the total acidity is controlled within the palatable range of 1.0-1.2g / 100g, and the taste is harmonious in terms of sweet, sour, salty and umami. The batch-to-batch variation CV is ≤3%, and the product consistency is excellent. The flavor retention rate is ≥91%. All indicators are significantly better than the comparative example.

[0118] 2. Example 4 (Simplified Scheme): Fermentation using only a single strain of lactic acid bacteria without acidity control resulted in significantly lower content of flavor substances (210 mg / kg) and number of volatile substances (62 types) compared to Examples 1-3. The total acid content was as high as 2.5 g / 100 g, with an excessively strong acidity and poor taste. This demonstrates that the multi-strain relay fermentation and acidity control steps of the present invention have a synergistic effect and are indispensable.

[0119] 3. Comparative Example 1 (Traditional Process): Fermentation cycle up to 6 months, low flavor compound content (92 mg / kg), large batch-to-batch variation (CV 23.5%), and total bacterial count >10. 4 The process requires the addition of 0.5 g / kg sodium benzoate at a CFU / g concentration. High-temperature sterilization results in significant flavor loss (only 58% retention rate), and the production cost is high, fully demonstrating the shortcomings of existing technologies.

[0120] 4. Comparative Example 2 (Single Strain, Non-Segmented Fermentation): Compared with Example 1, although Comparative Example 2 had the same total fermentation time, it did not use Aspergillus oryzae for koji making, did not introduce yeast, did not have aerobic / anaerobic alternation, and did not control acidity. Therefore, its total flavor compound content was only 145 mg / kg (34.5% of Example 1), and the number of volatile compounds was only 58 (60% of Example 1). The total acidity was as high as 2.0 g / 100 g (uncontrolled, resulting in an abrupt sour taste), requiring the addition of 0.2 g / kg sodium benzoate to inhibit the growth of other microorganisms. This fully demonstrates the importance and non-obviousness of the synergistic effect of the multi-strain relay fermentation system of this invention, which involves "Aspergillus oryzae koji making → lactic acid bacteria acid production → yeast aroma generation → aerobic / anaerobic alternation → acidity control."

[0121] In summary, the hot pot base and its preparation method based on microbial fermentation provided by this invention, through the synergistic effects of Aspergillus oryzae koji preparation, multi-strain fermentation of lactic acid bacteria and yeast, alternating aerobic / anaerobic temperature and humidity control, intelligent fermentation endpoint determination, acidity regulation, and low-temperature vacuum concentration combined with ultra-high pressure sterilization, successfully solves the key technical problems of traditional processes such as thin flavor, insufficient color, unbalanced acidity, significant safety hazards, and long production cycle. It has achieved unexpected technical effects and has significant progress and industrial applicability.

[0122] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing hot pot base based on microbial fermentation, characterized in that, Includes the following steps: S1. Raw material pretreatment: Crush broad beans to a particle size ≤1.5mm, inoculate with Aspergillus oryzae for koji fermentation to obtain broad bean koji material; melt butter in a 70-85℃ water bath and mix with an anti-caking agent; S2. Multi-strain relay fermentation: After mixing broad bean koji, butter and auxiliary materials such as chili and spices, lactic acid bacteria starter and yeast starter are inoculated in sequence, and staged temperature and humidity control and intermittent ventilation fermentation are carried out to obtain fermentation base material. S3. Fermentation endpoint determination: When the volatile flavor substances in the fermentation system reach a preset threshold, the fermentation is terminated. S4. Post-processing: The material after fermentation is terminated is concentrated under low temperature and vacuum, then filled into packaging containers and sealed. The sealed packaging is then sterilized to obtain the finished hot pot base.

2. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The Aspergillus oryzae strain used in step S1 for koji making and fermentation is Aspergillus oryzae Hu Niang 3.042; the lactic acid bacteria starter in step S2 includes Lactobacillus plantarum and Lactobacillus brevis, wherein the Lactobacillus plantarum strain is CICC 6240 and the Lactobacillus brevis strain is CICC 6239, with a live bacteria ratio of 2:1 to 4:1; the yeast starter includes Saccharomyces rouxii.

3. A method for preparing hot pot base based on microbial fermentation according to claim 1 or 2, characterized in that, The segmented temperature and humidity control and intermittent ventilation fermentation include: Lactic acid bacteria fermentation stage: control the temperature at 30-32℃, the relative humidity at 75-85%, and anaerobic fermentation for 24-30 hours; Yeast relay fermentation stage: After adding yeast starter, control the temperature at 28-32℃ and the relative humidity at 70-80%. Use intermittent ventilation fermentation, ventilating and stirring every 6-8 hours. After each ventilation and stirring, let it stand for anaerobic fermentation for 6-8 hours. Alternate between aerobic and anaerobic fermentation. The total fermentation time is 48-72 hours.

4. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, After determining the fermentation endpoint in step S3 and before the post-treatment in step S4, an acidity control step is also included: Salt and / or sugar are added to the fermentation substrate to control the acidity, so that the total acidity of the fermentation substrate is controlled at 0.8-1.5g / 100g and the salinity is controlled at 8-12%; the amount of salt added is 6-10% of the mass of the fermentation substrate and the amount of sugar added is 1-3% of the mass of the fermentation substrate.

5. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The fermentation endpoint was determined by using an electronic nose to detect the content of volatile compounds in the fermentation products, as well as the acid value and peroxide value. Fermentation was terminated when esters ≥12mg / kg, alcohols ≥8mg / kg, acid value ≤5mg / g, and peroxide value ≤0.25g / 100g. The detection results of the electronic nose were pre-calibrated using a gas chromatography-mass spectrometry system.

6. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The fermentation process is monitored and regulated by a fermentation control system, which includes: The sensor group, which includes a temperature sensor, an online pH detection module, and an ORP sensor, is used to collect temperature, pH value, and redox potential signals inside the fermenter. A programmable logic controller (PLC) is connected to the sensor group and each execution module, respectively, and is used to receive feedback signals from the sensor group, compare and calculate with a preset fermentation curve, and output control commands. The execution module includes a heating device, a humidifying device, and a ventilation device, which adjust the temperature, humidity, and ventilation volume inside the fermenter according to the control instructions output by the programmable logic controller; The human-machine interface is bidirectionally connected to the programmable logic controller and is used to display data, modify fermentation parameters, and provide alarm prompts. The electronic nose detection unit is activated when the fermentation endpoint is determined. It is used to detect the content of volatile flavor substances and feed the result back to the programmable logic controller. The programmable logic controller then decides whether to terminate the fermentation based on a preset threshold.

7. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The sterilization is ultra-high pressure sterilization, with the following conditions: pressure 550-650MPa, time 8-12 minutes. It can also be replaced by pulsed electric field sterilization or low-temperature plasma sterilization.

8. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The conditions for the low-temperature vacuum concentration are: temperature 45-55℃, vacuum degree -0.07 to -0.09MPa.

9. The method for preparing hot pot base based on microbial fermentation according to claim 1, characterized in that, The anti-caking agent is silicon dioxide, and the amount added is 0.05%-0.2% of the weight of the tallow.

10. A hot pot base based on microbial fermentation, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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