A method for brewing Luzhou-flavor liquor with strong flavor based on continuous fermentation

Abstract

The present application belongs to the technical field of liquor brewing, and particularly relates to a method for brewing Luzhou-flavor liquor based on continuous fermentation, which retains the main line of five-grain solid-state fermentation in pits, constructs an independent liquid continuous fermentation system mainly with Clostridium kluyveri, and stably produces fermentation liquor with a content of caproic acid of 3-8 g / L through membrane separation and backflow of bacteria; a multi-parameter online monitoring device is arranged in the pit, and during the esterification enzyme activity window period on the 10th-15th day of fermentation, the fermentation liquor is backfilled through a layered microporous pipeline closed loop according to real-time data of caproic acid ethyl ester in the pit; the brewing time is dynamically determined by comprehensively judging the change trend of caproic acid ethyl ester, the acid-ester ratio, total acid and total ester. The present application realizes continuous and stable production of caproic acid and precise flavor control, can improve the rate of high-quality base liquor, shorten the fermentation period, can be matched with yellow water resource utilization and multi-pit parallel mode, and is suitable for large-scale and intelligent production of Luzhou-flavor liquor.

Description

Technical Field

[0001] This invention belongs to the field of liquor brewing technology, specifically relating to a method for brewing liquor with a strong aroma based on continuous fermentation. Background Technology

[0002] Strong-aroma baijiu is beloved by consumers for its rich cellar aroma and mellow, sweet, and refreshing style. Its main aroma component is ethyl hexanoate. Traditional strong-aroma baijiu uses a solid-state fermentation process in mud pits. In these pits, hexanoic acid-producing bacteria (mainly Clostridium kluyveri and other Clostridium species) synthesize hexanoic acid using ethanol and acetic acid as substrates via a reverse β-oxidation pathway. Hexanoic acid then reacts with ethanol under the action of esterification enzymes to produce ethyl hexanoate.

[0003] However, in solid-state fermented mash, caproic acid bacteria are under multiple stresses such as low pH (which can drop to around pH 3.2 in the later stages of fermentation), high ethanol concentration, and high temperature fluctuations, and their acid production efficiency is far from reaching the theoretical optimal level. Moreover, the application methods of caproic acid bacteria liquid in the existing technology are mainly rinsing, filling, or one-time injection, which lacks the perception and feedback of the real-time flavor status in the main fermentation pit, making it difficult to determine the timing of fermentation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for brewing strong-aroma baijiu based on continuous fermentation. By appropriately decoupling hexanoic acid fermentation from the main fermentation system, adopting liquid continuous fermentation, and combining online monitoring and closed-loop recharge of the fermentation pits, the problem of low hexanoic acid fermentation efficiency in the prior art is solved.

[0005] The specific technical solution adopted by this invention is as follows: A method for brewing a strong-aroma baijiu based on continuous fermentation includes the following steps: Step S1: Traditional Solid-State Fermentation Mainline Using sorghum, rice, glutinous rice, wheat, and corn as raw materials, the process involves ingredient mixing, grain moistening, steaming, and cooling. A mixture of medium-high temperature starter culture (Daqu) and functional starter culture (high temperature starter culture or enhanced starter culture) is then added, with a mass ratio of (10-5):1. The mixture is then placed in a mud pit for solid-state fermentation. The pit temperature is controlled at 20-24℃.

[0006] Step S2: Construct an independent liquid continuous fermentation system Using artificially prepared liquid culture medium containing carbon and nitrogen sources as the substrate (no more than 30% yellow water can be added as a supplementary nutrient source, but the lactic acid content must be controlled to not exceed 2g / L), and Clostridium kluyveri as the main inoculum, continuous culture is carried out in a fermenter. The fermenter is equipped with a stirring device, a temperature control jacket, an automatic pH adjustment device, an anaerobic maintenance device, and a membrane separation unit.

[0007] Cell reflux is achieved through membrane separation to maintain cell density within the reactor. Operating parameters are: pH 6.0-7.5, temperature 30-37℃, hydraulic retention time 48-96 hours, cell reflux ratio 30%-60%, anaerobic conditions. Hexanoic acid content in the fermentation broth is controlled at 3-8 g / L.

[0008] It should be noted that hexanoic acid concentrations exceeding 8-10 g / L can inhibit bacterial metabolism. When the online detection shows hexanoic acid levels approaching 8 g / L, the control system automatically increases the feed rate to dilute the fermentation broth, maintaining the hexanoic acid concentration below the inhibitory level.

[0009] Step S3: Online monitoring of the fermentation pit Temperature sensors (3-5 points), moisture sensors (2-3 points), acidity sensors (1-2 points), and sampling and analysis devices are installed in each fermentation pit. The sampling and analysis device includes a sampling probe embedded in the pit and an external gas chromatograph. Liquid or gas samples are extracted from the gaps between the mash and fermentation grains using the sampling probe. Sampling frequency is 6-12 hours per sample, and the average of three parallel samples is taken for each test to eliminate the influence of local fluctuations. The detection parameters include at least the ethyl hexanoate concentration. All data is uploaded to the central control system in real time.

[0010] Step S4: Closed-loop recharge The central control system has a pre-set target range for ethyl hexanoate (preferably 3.0-4.5 g / L). Since the formation of ethyl hexanoate is limited by esterification enzyme activity, the reinjection timing should be limited to the window period of high esterification enzyme activity (days 10-15 of fermentation). When the real-time monitoring value falls below the target lower limit, the system automatically starts the reinjection pump, drawing fermentation broth from the storage tank of the liquid continuous fermentation system and injecting it in layers through multiple microporous pipes pre-embedded at different heights on the pit wall (0.3m, 0.8m, and 1.3m from the pit bottom). Each layer of pipes has 4-6 injection points evenly distributed around the pit wall to disperse the fermentation broth as much as possible. The reinjection volume is 0.5%-5% of the mash mass.

[0011] It should be noted that the liquid diffusion coefficient of solid mash is low, making it difficult to achieve uniform distribution through single-point reinjection. This method employs a layered, multi-point injection approach, injecting small amounts in stages (total reinjection time 40-60 minutes) to mitigate the problem of uneven mass transfer.

[0012] Step S5: Dynamic Determination of Storage The quality of strong-aroma baijiu is determined by a variety of flavor compounds, and a single indicator cannot guarantee the quality of the liquor. When the central control system comprehensively judges that the following indicators meet the preset standards, it issues a recommendation to remove the liquor from the cellar: the ethyl hexanoate content decreases or tends to plateau twice consecutively (with an interval of 24 hours), the ethyl acetate / ethyl hexanoate ratio is between 1:1.2 and 1.8, the total acid is ≥1.8g / L, and the total esters are ≥4.0g / L. After the comprehensive weighted score reaches the preset threshold, the operator confirms and executes the decision.

[0013] Furthermore, yellow liquid, not exceeding 30% of the total volume of the culture medium, can be added to the substrate as a supplementary nutrient source. When adding yellow liquid, the lactic acid content in the culture medium should be controlled to not exceed 2g / L.

[0014] The yellow water pumped from the pit is sterilized and replenished to partially replace the water used in the culture medium. The replacement ratio shall not exceed 20% of the total volume of the culture medium, and the number of times a single batch of yellow water is recycled shall not exceed 2.

[0015] The liquid continuous fermentation system is connected in parallel with multiple fermentation pits. The central control system distributes fermentation liquid to each fermentation pit in stages or simultaneously based on real-time monitoring data of different fermentation pits.

[0016] The technical effects achieved by this invention are as follows: This invention provides a method for brewing strong-aroma baijiu based on continuous fermentation, upgrading hexanoic acid fermentation from batch to continuous. By maintaining cell density through cell reflux, the hexanoic acid yield can reach 3-8 g / L, and the system can operate stably for 10-15 days. Refilling is limited to the 10th-15th day of fermentation (the period of high esterase activity), which matches the supply of hexanoic acid substrate with esterification capacity, improving the efficiency of ethyl hexanoate production. The decision to remove the product from the fermentation pit no longer relies on a single indicator or a fixed period, but is based on a weighted judgment of multiple indicators such as ethyl hexanoate, ethyl acetate / ethyl hexanoate ratio, total acid, and total esters, making the recommendation to remove the product from the fermentation pit more scientific. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention. Example

[0019] like Figure 1 As shown, a method for brewing a strong-aroma baijiu based on continuous fermentation includes the following steps: Step S1: Traditional Solid-State Fermentation Mainline The formula consists of five grains (36% sorghum, 22% rice, 18% glutinous rice, 16% wheat, and 8% corn). After mixing, moistening, steaming, and drying, a mixture of medium-high temperature starter and functional starter (high temperature starter) (mass ratio 8:1) is added. The mixture is then placed in a mud pit for solid-state fermentation at a temperature of 22℃.

[0020] Step S2: Construction of the liquid continuous fermentation system The selected bacterial strain was Clostridium kluyveri for inoculation.

[0021] The culture medium was mainly a liquid medium containing carbon and nitrogen sources prepared artificially, with 25% yellow water added (the yellow water was sterilized and the lactic acid content was controlled below 1.8 g / L), and 3% (v / v) ethanol and 0.5% (w / v) sodium acetate added to adjust the pH to 6.5.

[0022] It adopts a 500L stirred fermenter, equipped with an automatic pH adjustment device, temperature control jacket, anaerobic maintenance device and membrane separation unit.

[0023] The operating parameters of the stirred fermenter were: pH 6.5±0.2, temperature 34±1℃, stirring speed 50 rpm, anaerobic conditions (continuous nitrogen gas introduction), hydraulic retention time 72 hours, and cell reflux ratio 50%. After the system stabilized, the average hexanoic acid content in the fermentation broth was 5.8 g / L. When the hexanoic acid content approached 8 g / L, the feed rate was automatically increased for dilution.

[0024] Steps S3-S4: Cellar monitoring and closed-loop recharge Temperature sensors (3 points), moisture sensors (2 points), acidity sensors (1 point), and sampling probes were installed inside the mud pit. The concentration of ethyl hexanoate was measured every 12 hours using an external gas chromatograph (average of 3 parallel samples each time). The central control system was preset to a target range of 3.5-4.2 g / L for ethyl hexanoate.

[0025] On the 12th day of fermentation, the ethyl hexanoate content in the pit was detected to be 2.8 g / L. The system automatically started the reinjection pump and injected 60 kg of fermentation liquid (about 3% of the mash mass) in batches through microporous pipes (4 injection points per circumference per layer) at different heights in the pit wall. The total reinjection time was 50 minutes.

[0026] Step S5: Dynamic Removal from the Cellar On the 55th day of fermentation, the ethyl hexanoate content in the cellar decreased twice (4.0→3.7→3.5 g / L), the ethyl acetate / ethyl hexanoate ratio was 1:1.50, the total acid was 2.1 g / L, the total ester was 4.3 g / L, the overall score met the standards, and the system issued a recommendation to remove the product from the cellar. After confirmation by the operator, the removal from the cellar was carried out.

[0027] Testing revealed that the ethyl hexanoate content in the base liquor of the experimental group reached 3.65 g / L, with a superior grade rate of 76%. The control group (which did not use this system and underwent traditional solid-state fermentation in mud pits) had an ethyl hexanoate content of 2.45 g / L, with a superior grade rate of 58%. Example

[0028] The difference between this embodiment and Embodiment 1 lies in the fact that the liquid continuous fermentation system in this embodiment is connected in parallel with 10 mud pits (each 15m³). The central control system distributes the fermentation liquid in stages based on real-time monitoring data from different pits.

[0029] Meanwhile, in this implementation, the yellow water pumped from each pit will be collected, sterilized, and partially used to replace the water in the culture medium (replacement ratio 15%). Each batch of yellow water will be recycled twice before being discharged for treatment.

[0030] After three complete fermentation cycles (a total of 30 fermentation pits), the statistical results showed that the average ethyl hexanoate content was 3.55 ± 0.28 g / L. The average rate of superior grade products was 74.5% ± 3.5%, and the average fermentation cycle was 56 ± 5 days. Example

[0031] This embodiment discloses a system for implementing the above-mentioned intelligent brewing method for strong-aroma baijiu based on continuous liquid fermentation. The system includes a continuous liquid fermentation subsystem, an online monitoring subsystem for fermentation pits, a closed-loop recharge subsystem, and a central control subsystem.

[0032] The liquid continuous fermentation subsystem uses an artificially prepared liquid culture medium containing carbon and nitrogen sources as a substrate (with up to 30% yellow water added), and Clostridium kluyveri as the main inoculum, for continuous cultivation in a fermenter. Cell reflux is achieved through a membrane separation unit to produce a fermentation broth rich in hexanoic acid. Specifically, the liquid continuous fermentation subsystem includes: Substrate storage tanks are used to store culture media; when adding yellow liquid, the lactic acid content must be controlled to not exceed 2g / L.

[0033] The fermenter is equipped with a stirring device, a temperature control jacket, an automatic pH adjustment device, and an anaerobic maintenance device. Operating parameters are: pH 6.0-7.5, temperature 30-37℃, and hydraulic retention time 48-96 hours.

[0034] A feed pump, connected to the substrate storage tank and the fermentation tank, is used to continuously transport the substrate to the fermentation tank.

[0035] A membrane separation unit is connected to the discharge end of the fermenter to separate the bacterial cells from the fermentation broth, with a reflux ratio of 30%-60%.

[0036] The cell reflux pipeline connects the cell concentrate outlet of the membrane separation unit to the feed inlet of the fermenter.

[0037] The fermentation broth collection pipeline connects the filtrate outlet of the membrane separation unit to the fermentation broth storage tank of the closed-loop recharge subsystem.

[0038] The liquid continuous fermentation subsystem can operate stably for 10-15 days, with the hexanoic acid content in the fermentation broth controlled at 3-8 g / L. When the hexanoic acid content is detected online to be close to 8 g / L, the control system automatically increases the feed rate to dilute the fermentation broth.

[0039] The online monitoring subsystem for the fermentation pit is installed inside the pit and is used to collect real-time data on the temperature, moisture content, acidity, and ethyl hexanoate concentration of the mash within the pit. Specifically, the online monitoring subsystem for the fermentation pit includes: Temperature sensors are installed at 3-5 monitoring points along the longitudinal direction of the pit.

[0040] Moisture sensor, set up 2-3 monitoring points.

[0041] Acidity sensor, set up 1-2 monitoring points.

[0042] The sampling and analysis device includes a sampling probe embedded in the cellar and an external gas chromatograph. The sampling frequency is 6-12 hours / time, and the average value of 3 parallel samples is taken for each test.

[0043] All of the aforementioned sensors and analyzers are connected to the central control subsystem.

[0044] The closed-loop recharge subsystem is used to quantitatively recharge the fermentation broth produced by the liquid continuous fermentation subsystem back into the fermentation pit. Specifically, the closed-loop recharge subsystem includes: The fermentation broth storage tank is connected to the fermentation broth collection pipeline of the liquid continuous fermentation subsystem.

[0045] The reinjection pump connects the fermentation broth storage tank and the reinjection pipeline and is controlled by the central control subsystem.

[0046] The micro-pore reinjection pipes are pre-embedded at different heights in the cellar wall (0.3m, 0.8m, and 1.3m from the bottom of the cellar). Each layer of pipes has 4-6 injection points evenly distributed around the cellar wall, and the pipes are covered with micropores with a diameter of 0.5-2mm.

[0047] The reinjection pipeline connects the reinjection pump to the microporous reinjection pipe. The reinjection amount is 0.5%-5% of the mash mass, and the reinjection time is limited to the 10th-15th day of fermentation.

[0048] The central control subsystem is communicatively connected to the liquid continuous fermentation subsystem, the online monitoring subsystem for the fermentation pits, and the closed-loop recharge subsystem. Specifically, the central control subsystem includes: The data acquisition module is used to receive real-time monitoring data such as temperature, moisture, acidity, and ethyl hexanoate concentration.

[0049] The storage module is used to store historical fermentation data and preset target range parameters.

[0050] The recharge control module is communicatively connected to the recharge pump and is used to automatically control the recharge based on the deviation between the measured value and the preset target range.

[0051] The cellar exit judgment module is used to comprehensively evaluate multiple physicochemical indicators and issue a cellar exit recommendation when a preset threshold is reached.

[0052] The display and interaction module is used to display real-time monitoring data and system operating status, and provides a manual confirmation interface.

[0053] The system may also include a partial recycling unit for yellow water, which includes a yellow water collection tank, a sterilization device, and a feeding device. The yellow water pumped from the pit is sterilized and fed with feed to partially replace the water used in the culture medium (the replacement ratio does not exceed 20%). The number of times a single batch of yellow water is recycled does not exceed 2 times.

[0054] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method for brewing a strong-aroma baijiu based on continuous fermentation, characterized in that: Includes the following steps: Step S1: Using sorghum, rice, glutinous rice, wheat, and corn as raw materials, after mixing, moistening, steaming, and drying, a mixture of medium-high temperature Daqu and functional Daqu is added, and the mixture is put into a mud pit for solid-state fermentation. Step S2: Using artificially prepared liquid culture medium containing carbon and nitrogen sources as substrate, and Clostridium kluyveri as the main strain, the culture is continuously carried out in a fermenter. Cell reflux is achieved through membrane separation. Under anaerobic conditions of pH 6.0-7.5, 30-37℃, the fermentation broth rich in hexanoic acid is continuously produced. The hexanoic acid content in the fermentation broth is controlled at 3-8 g / L. Step S3: Monitor the temperature, moisture, acidity, and ethyl hexanoate concentration of the mash in the pit online; Step S4: During the 10th-15th day of fermentation, the fermentation liquid is reinjected into the fermentation pit at a rate of 0.5%-5% of the mash mass. Step S5: When the ethyl hexanoate content decreases or plateaus twice consecutively, the ethyl acetate / ethyl hexanoate ratio is between 1:1.2 and 1.8, the total acid is ≥1.8 g / L, and the total ester is ≥4.0 g / L, it is determined that the kiln can be discharged.

2. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: In step S1, the mass ratio of medium-high temperature Daqu to functional Daqu is 10-5:

1.

3. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: The weight percentages of sorghum, rice, glutinous rice, wheat, and corn are as follows: Sorghum 36%, rice 22%, glutinous rice 18%, wheat 16%, corn 8%.

4. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: In step S2, the bacterial cell reflux ratio is 30%-60%, and the hydraulic retention time is 48-96 hours.

5. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: In step S3, online monitoring is performed using a sampling and analysis device. The sampling and analysis device includes a sampling probe embedded in the cellar and an external gas chromatograph. The sampling probe is used to extract liquid or gas samples from the gaps between the mash and the fermentation mash. The sampling frequency is 6-12 hours / time, and the average value of 3 parallel samples is taken for each test.

6. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: In step S4, the recharge is injected in layers through multiple micro-perforated pipes pre-embedded at different heights in the cellar wall.

7. The method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: No more than 30% of the total volume of the culture medium is added to the substrate as a supplementary nutrient source, and the lactic acid content in the culture medium is controlled not to exceed 2g / L when adding the yellow water.

8. A method for brewing a strong-aroma baijiu based on continuous fermentation according to claim 1, characterized in that: Also includes: The yellow water pumped from the pit is sterilized and replenished to partially replace the water used in the culture medium. The replacement ratio shall not exceed 20% of the total volume of the culture medium, and the number of times a single batch of yellow water is recycled shall not exceed 2.

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