Production method of high-grade flavoring liquor of Luzhou-flavor liquor

Abstract

The invention discloses a production method of high-grade flavoring liquor of Luzhou-flavor liquor, and relates to the field of liquor brewing. Aiming at the problems of insufficient substrate conversion, easy unbalance of flavor and easy rancidification of fermentation in the traditional double-round fermentation process, the technical scheme of combining double-round fermentation of 15-20% of fermented grains at the bottom of a cellar, mother grain acidity / starch double-index screening, precise regulation and control of sterile air in three-round fermentation / feeding before entering the cellar, and segmented distillation and graded storage is adopted. The process can improve the fermented grain conversion efficiency and stabilize the acidity of a fermentation system; the content of characteristic flavor substances such as ethyl hexanoate is greatly increased, and the flavor ratio is balanced; the sensory quality of raw wine is improved, and the cellar aroma and the ester aroma are stronger. The technological parameter range is feasible through experimental verification, the technical effect is obviously superior to that of a traditional technology, and the method is suitable for producing high-quality Luzhou-flavor liquor.

Description

Technical Field

[0001] This invention relates to the field of strong-aroma baijiu brewing technology, and specifically proposes a method for producing high-grade flavoring liquor from strong-aroma baijiu. Background Technology

[0002] As one of the mainstream baijiu aroma types in my country, the core flavor and quality of strong-aroma baijiu rely on the metabolic activities of the microbial community and the accumulation of flavor substances (such as ethyl hexanoate and ethyl butyrate) during the fermentation process in the fermentation pits. Currently, the industry generally adopts a double-stage fermentation process to enhance the flavor of the baijiu. This process involves retaining 15%-20% of the mash at the bottom of the fermentation pit for two rounds of fermentation (the total cycle is about 140 days), extending the contact time between the mash and the pit mud to promote the synthesis of esters.

[0003] However, the existing double-stage fermentation process has significant technical bottlenecks: First, there is an upper limit to the accumulation of flavor substances. Due to the limitations of the fermentation cycle and microbial activity, the ethyl hexanoate content of the raw liquor from double-stage fermentation is usually below 800 mg / L, which is insufficient to meet the demand for rich flavor in high-end strong-aroma baijiu. Second, blindly extending the fermentation cycle to three stages can easily lead to excessive proliferation of lactic acid bacteria in the fermentation pit, resulting in a sharp increase in the acidity of the mash (pH < 3.5), hydrolysis of esters, and a spoilage rate of over 12%. This has led to a technical prejudice in the industry that "three-stage fermentation inevitably leads to spoilage." Third, microbial control relies on experience-based operation and lacks understanding of the oxidation-reduction processes within the fermentation pit. Precise control of the original environment and nutrient supply can easily inhibit the activity of caproic acid bacteria (key bacteria for ester synthesis), and the proportion of lactic acid bacteria often exceeds 25%, leading to an imbalance in the microbial community and an increase in off-flavors in the liquor. Fourth, the distillation process often adopts whole distillation or rough grading methods, without designing distillation strategies based on the distribution characteristics of flavor substances in the three-stage fermentation mash. Off-flavor substances such as higher alcohols and aldehydes in the first batch of liquor are mixed into the base liquor, resulting in a noticeable bitterness. Fifth, uneven distribution of koji during the preparation of mother mash and unstable anaerobic environment in the fermentation pit result in a koji utilization rate of less than 60%, and insufficient interaction efficiency between the mash and the pit mud, further limiting the synthesis of flavor substances.

[0004] In summary, the existing brewing process for strong-aroma baijiu is insufficient to achieve a balance of microbial communities and synergistic transformation of flavor substances while extending the fermentation cycle. There is an urgent need for a three-stage fermentation brewing process that can overcome technical biases and achieve precise control in order to solve the common problems in the industry such as "insufficient flavor, easy fermentation spoilage, and reliance on experience in control". Summary of the Invention

[0005] In view of this, the present invention proposes a production method for high-grade flavoring liquor of strong-aroma baijiu. By optimizing the fermentation cycle control, precisely regulating microorganisms, and employing distillation and grading strategies, the method achieves efficient accumulation and synergistic transformation of flavor substances while avoiding spoilage of the mash.

[0006] The technical solution of this invention is implemented as follows: This invention provides a method for producing a high-grade flavoring liquor of strong-aroma baijiu, comprising the following steps: (1) Preparation of double-round fermentation of yeast mash: Take the mash from the bottom 15-20% height of the fermentation pit of strong aroma baijiu (Note: the fermentation pit is a mud pit with a mud thickness of 8-12cm and a pH value of 6.5-7.5), add strong aroma baijiu daqu at 7.5kg / boiler (addition amount 0.625-1.25kg / 100kg mash), and sprinkle the daqu twice: after the first sprinkling of daqu, stir on both sides for 5-8min, after the second sprinkling of daqu, compact the mash into shape, and lay a 1.8-2.2cm thick layer of steamed (30±5min) cooked rice husk on top (only as a physical isolation layer), and carry out double-round fermentation (each round cycle is 70±5 days, the total cycle is 140 days) to obtain double-round fermentation of yeast mash; (2) Screening of mother mash quality: The qualified mother mash is screened by sensory and physicochemical dual standards. Specifically, mother mash with acidity < 4.5 mmol / 10g mash and starch residue < 10wt% is screened (the residue and reducing sugar content of the double fermentation mash are low, and no additional carbon source is required). (3) Three-round fermentation: The qualified mother mash is transferred to the mud pit (Note: the mash from the three-round fermentation is located at the bottom 15-20% of the pit height, with the regular first-round mash above it. The entire pit is filled to the brim, with no top gas phase voids). The total fermentation cycle is 70±5 days. The total fermentation cycle for the two-round and three-round fermentation is 210 days (the mash is not removed during fermentation). This includes microbial community control operations. During the early fermentation period (0-60 days), sterile air is not introduced. The initial oxygen content is consumed by the natural growth and reproduction of the initial microorganisms (such as caproic acid bacteria and yeast) in the mash, which causes the oxidation-reduction potential (Eh) in the pit to naturally drop to -200~-250mV, maintaining the pH in the pit at 3.5-4.2. During the later stage of fermentation (60-70 days): Sterile air is continuously introduced into the fermentation pit (preparation method: compressed air is sequentially filtered through 0.1μm activated carbon, sterilized by 254nm ultraviolet light for 30±5s, and dried at a dew point ≤-40℃). The oxygen volume concentration in the gas phase space of the pit is controlled to be 0.8-1.2% through bottom micropore aeration (to activate the activity of hexanoic acid bacteria ester synthase and inhibit lactic acid bacteria acid production). Feeding steps: Before the fermented mash from the third round is put into the pit, add nutrient supplement (glucose to yeast extract in a mass ratio of 3:1) to the qualified mother mash. The amount added is 1.0-1.5% of the qualified mother mash mass (this stage is the early stage of microbial proliferation, which can specifically meet the needs of caproic acid bacteria for acetyl coenzyme A and avoid the proliferation of miscellaneous bacteria or the generation of higher alcohols). Monitoring requirements: The concentration of gaseous oxygen in the fermentation pit is monitored at one point in the middle of the mash after three rounds of fermentation using a portable oxygen detector (model: GXH-3011A), and is monitored once every 24 hours; the oxidation-reduction potential (Eh) is monitored in the middle layer of the mash using a portable potentiometer (model: PHB-4), and is monitored once every 12 hours, ensuring that Eh drops to -200~-250mV in the early stage and is maintained at -150~-200mV in the later stage. (4) Distillation: The mash after three rounds of fermentation is distilled in stages. The temperature of the still is controlled at 95-100℃, the distillation rate is fixed at 2L / min, a slow-fire distillation method is adopted, and the steam pressure is maintained at 0.02MPa. The specific stage standards are as follows: (a) First distillate collection: The fraction with an alcohol content of 66-76 vol% at a standard temperature of 20℃ is collected as the first distillate (heads), and the collection amount is 4-6% of the total distillate volume, which is used as flavoring wine; (b) Collection of mid-section liquor: The fraction with an alcohol content of 65-75 vol% at a standard temperature of 20℃ is collected as the mid-section liquor (main liquor), and the collection volume is 55-65% of the total distillate volume, which is the core source of high-quality base liquor; (c) Collection of tail liquor: The fraction with an alcohol content of 40-65 vol% at a standard temperature of 20℃ is collected as tail liquor, and the collection amount is 29-41% of the total distillation volume. It is used for the next still distillation to enhance the aroma. (5) Graded storage: The middle section of the liquor is transferred to a 200L ceramic jar and sealed for storage (each jar contains 180L of liquor). The storage environment temperature is 20-24℃ and the relative humidity is 65-75%. The storage time is ≥3 years (the micropores of the ceramic jar enable "micro-breathing" and promote the aging of the liquor). The first section of liquor is kept separately as a flavoring liquor, and the last section of liquor is used for re-steaming and does not directly participate in the blending of the base liquor.

[0007] The present invention has the following advantages over the prior art. The three-stage fermentation process for strong-aroma baijiu proposed in this application exhibits significant and comprehensive technical advantages compared to the traditional two-stage fermentation process. In terms of mash fermentation and conversion, this three-stage fermentation process can more fully utilize substrates such as starch in the mash, with an average starch residue of 10.62% (10.5% lower than the 11.87% in two-stage fermentation) and an average reducing sugar residue of 0.38% (lower than the 0.48% in two-stage fermentation). Furthermore, it can stabilize the acidity of the mash within the range of 3.42-4.44 mmol / 10g, avoiding the acidity imbalance that occurs under high feed addition or high sterile air conditions in two-stage fermentation (e.g., the acidity reaches 4.51 mmol / 10g in the 0.8% oxygen concentration group of two-stage fermentation). This results in superior fermentation system stability and substrate conversion efficiency.

[0008] In terms of the flavor and quality of the raw liquor, the ethyl hexanoate content of each group of raw liquor produced by the three-round fermentation process was above 910.26 mg / 100 mL, with the optimal group (1.0% feed addition + 0.8% oxygen concentration) reaching 1242.21 mg / 100 mL (an increase of 106.8% compared to the 600.75 mg / 100 mL of the two-round fermentation group with the same parameters). At the same time, a balanced ratio of ethyl hexanoate to ethyl acetate was achieved, with an average ratio of 1.52 (within the reasonable range of 1.2-2.2 for high-quality strong-aroma baijiu), avoiding the flavor imbalance commonly found in the two-round fermentation process (where the ratio of ethyl hexanoate to ethyl acetate was as low as 0.53 in some groups). The fusel oil content averaged 15.7 mg / 100 mL (lower than 21.3 mg / 100 mL in the two-round fermentation process), effectively reducing the risk of bitterness and off-flavors.

[0009] In terms of sensory quality, the average sensory score of the raw liquor from the three-round fermentation process was 92.6 points (an improvement of 1.1 points compared to 91.6 points from the two-round fermentation process). The full-process synergistic group (7.5kg of koji + 1.0% supplementary feed + 0.8% oxygen concentration) scored 94 points, with comments describing it as having "rich cellar aroma and ester fragrance, full-bodied sweetness, and a clean finish with a lingering aftertaste." The koji optimization group (10kg of koji added + 0.8% oxygen concentration) scored 93.1 points (an improvement of 2.9 points compared to 90.5 points from the two-round fermentation group with the same parameters), compensating for the burnt flavor defect caused by the high koji dosage in the two-round fermentation process. In addition, all core parameters have been experimentally verified to be feasible, providing a reliable path for simultaneously improving the quality and fermentation efficiency of strong-aroma baijiu. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a structural diagram of the cellar of the present invention.

[0012] In the diagram: 1- Pit, 2- Aeration micropores, 3- Gas passage, 4- Three-stage fermentation mash, 5- Oxygen concentration sensor. Detailed Implementation

[0013] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0014] To clarify the process differences among the various embodiments, unified baseline conditions are first defined: the pit volume is 10m³, the mother mash is high-quality pit mud mother mash that has been continuously fermented for 3 rounds (initial value of lactic acid bacteria ratio is 12%, initial value of hexanoic acid bacteria ratio is 20%), the fermentation temperature is controlled at 28-32℃, the distillation is atmospheric pressure distillation (distillation temperature 78-82℃), the starter culture is medium-high temperature Daqu (saccharification power 500U / g), the feed is a nutrient feed with a glucose to yeast extract mass ratio of 3:1 (reducing sugar content 15%), and the aseptic air control adopts the bottom aeration micropore aeration method of the pit.

[0015] In the following specific embodiments, "effective fermentation volume of the fermentation pit" refers to the initial filling volume of the mash when it is put into the pit, calculated as "cross-sectional area of ​​the pit × filling height of the mash", excluding the void at the top of the pit; "alcohol content" refers to the alcohol content value measured at a standard temperature of 20°C. Example Group 1: Basic Three-Round Fermentation Process Example 1-1: Simple Three-Round Fermentation Process Preparation steps Preparation of mother mash for three rounds of continuous fermentation Round 1 conventional fermentation - retention (1) Raw material selection: Take 800 kg of mash from the bottom 15-20% of the height of the newly fed grain pit. The initial sensory screening shows that it has a strong mash aroma and is free from mold and caking. The physicochemical test shows that the moisture content is 62%, the acidity is 3.5 mmol / 10g, and the starch content is 13 wt%. (2) Adding koji: Add medium-high temperature koji (crushed to 80 mesh) at a ratio of 7.5 kg / 800 kg of mash, sprinkle the koji twice and stir on both sides for 5 minutes each time, and control the material temperature at 28℃; (3) Anaerobic construction: After compaction and shaping, a 2cm layer of steamed bran is laid, and 800kg of conventional first-round fermented mash is covered on top and compacted. A monitoring probe is pre-embedded. (4) Fermentation and retention: Control the cellar temperature at 28-32℃ for 70 days of fermentation. After leaving the cellar, do not distill. Only retain 15-20% of the mash at the bottom of the cellar. At this time, the mother mash contains 15% hexanoic acid bacteria and 18% lactic acid bacteria.

[0016] Second round of conventional fermentation - retention (1) Remixing the starter culture: Take 800 kg of the mother mash left from the first round, add 7.5 kg of new starter culture powder, repeat the double-sided mixing operation, and control the material temperature ≤30℃; (2) Anaerobic fermentation: The mash is compacted, covered with rice husks, and pressed into the pit in the same manner, and fermented for 70 days; (3) Retention and screening: After leaving the pit, the bottom of the pit was retained and tested. The results showed that the content of hexanoic acid bacteria was 18%, the content of lactic acid bacteria was 15%, the moisture content was 63%, the acidity was 3.8 mmol / 10g, and the starch content was 12 wt%.

[0017] Third round of conventional fermentation - retention (1) Final compounding: Take 800 kg of the mother mash left over from the second round, add 7.5 kg of Daqu powder again and homogenize and mix; (2) Deep fermentation: repeated anaerobic construction and 70-day fermentation operation, with no opening of the lid throughout the process; (3) Retain for later use: After the fermentation is completed, the fermented mash at the bottom of the pit is retained, which is the "mother mash that has been fermented for 3 consecutive rounds". At this time, the microbial community and physicochemical indicators of the mother mash are initially stable.

[0018] 1. Screening of mother mash: Select mother mash from three consecutive fermentations, remove impurities, and crush to a particle size of 2-5mm. The initial lactic acid bacteria content is 12%, and the caproic acid bacteria content is 20%. 2. Mixing the starter culture: After crushing 7.5 kg of medium-high temperature starter culture, mix it evenly with 800 kg of mother mash, and control the material temperature at 28℃. Use a layered starter culture sprinkling and cross-stirring method. First, spread the mash into a 20 cm thick layer, sprinkle 30% starter culture powder and stir longitudinally for 3 minutes. Then spread the second layer of mash and sprinkle 30% starter culture powder, stir laterally for 3 minutes. Finally, sprinkle the remaining 40% starter culture powder on the surface and stir the whole thing for 5 minutes to ensure that the starter culture content deviation per gram of mash is ≤5%.

[0019] 3. Fermentation in a cellar: (1) Pretreatment of the pit: mud pits (pit volume 10m³) are selected. 3 Clean the inner wall of the pit in advance to ensure that the pit mud is of uniform thickness (8-12cm), test the pH value of the pit mud to be 6.5-7.5, the proportion of caproic acid bacteria ≥20%, and there is no crusting or shedding; spray 5L of sterile water evenly on the bottom of the pit (to keep the pit mud moist and prevent the mash from losing water), and control the initial temperature of the pit to 26-28℃.

[0020] (2) Layering of mash into the pit: 800 kg of mash mixed with yeast is placed into the pit in 3 layers, each layer about 30 cm thick. After each layer is laid, it is lightly compacted with a pit treading tool (compacted density 1.1-1.2 g / cm³). 3 To avoid forming large pores, after all three layers are placed in the pit, the surface of the mash is leveled to ensure that the gap between the mash and the pit wall is ≤2cm (to prevent oxygen leakage at the edges).

[0021] (3) Covering and sealing with cellar mud: Take high-quality cellar mud (the same type as the cellar), roll it into mud cakes with a thickness of 5cm, and evenly cover the surface of the mash. The edge of the mud cake extends to the cellar wall and fits tightly with the cellar mud to form a “mash-cellar mud” sealing layer. Then, spread a 2cm thick layer of steamed cooked rice husks (steamed for 30 minutes to remove pentosans) on the surface of the cellar mud to further isolate the air.

[0022] (4) Conventional fermented mash pressing: Cover the top of the bran layer with 800 kg of conventional first-cycle fermented mash (fermentation cycle of 70 days), and compact it in two layers. The compacted thickness accounts for 60% of the height of the upper part of the pit, forming a four-layer sealed structure of "conventional fermented mash - bran - pit mud - mother mash" to prevent the intrusion of external air.

[0023] (5) The fermentation process is controlled in stages (70 days, without removing the mash midway). ① First 15 days (microbial adaptation period): Maintain the temperature of the pit at 28-29℃, monitor the gas phase oxygen concentration using a pre-embedded GXH-3011A oxygen detector, and ensure that it drops from the initial 0.5% to <0.05% within 15 days; monitor the Eh value from -150mV to -200mV using a PHB-4 potentiometer. This stage is the microbial colonization period, and no intervention is required.

[0024] ②15-45 days (microbial proliferation period): Raise the cellar temperature to 30-31℃ to promote the proliferation of functional bacteria such as caproic acid bacteria and yeast; every 10 days, take 10g of mash through a pre-embedded sampling tube for testing to ensure that the acidity is stable at 3.8-4.0mmol / 10g and the starch degradation rate is 0.05wt% / day. If the acidity is >4.0mmol / 10g, adjust the cellar temperature (lower to 29℃) to inhibit the reproduction of lactic acid bacteria.

[0025] ③ 45-70 days (ester precursor accumulation period): The fermentation temperature is maintained at 31-32℃ to enhance the synthesis of ester precursors such as alcohols and organic acids; at the end of 70 days of fermentation, the mash indicators are tested: moisture 63%, acidity 4.2mmol / 10g, starch 10.5wt%, hexanoic acid bacteria 22%, lactic acid bacteria 15%, no rancid odor, and the first round of fermentation is completed.

[0026] 4. Re-fermentation in the pit: (1) Removal of conventional mash and pit mud: After fermentation, first gently remove the top 800 kg of conventional mash layer by layer (to avoid disturbing the mother mash), then carefully scrape off the top 5 cm of pit mud and 2 cm of chaff, and collect them for later use (for subsequent three rounds of sealing); throughout the operation, keep the temperature inside the pit ≥ 28℃ to prevent the mash temperature from dropping suddenly and causing the microbial community to become inactive.

[0027] (2) Turning the mash in the whole pit: adopt the turning method of "from the edge to the center and from the bottom to the surface" to turn up all the mash after the first fermentation. The turning tool should be inserted into the pit mud layer (10cm) to make the bottom bacteria fully mixed with the mash. During the turning process, the material temperature should be controlled to ≤32℃. If the material temperature is too high, stop turning and cover with wet rice husks to cool down (to avoid premature deactivation of the starter). The overall turning time is 8-10 minutes to ensure that the mash is homogeneous and free of lumps.

[0028] (3) Add koji and homogenize: Add new medium-high temperature koji powder (crushed to 80 mesh) at a ratio of 7.5 kg / boiler (800 kg of mash), sprinkle it evenly on the surface of the mash after stirring, stir again for 5 minutes to ensure that the koji and mash are in full contact; after adding koji, the material temperature is 28-30℃, which meets the requirements for re-fermentation temperature.

[0029] (4) Reseal and construct an anaerobic environment ① First, level and compact the fermented mash (restoring its density to 1.1-1.2 g / cm³). 3 Then, the 5cm of pit mud removed in the first round is re-covered on the surface and sealed. ② Spread a 2cm layer of freshly steamed bran husks, cover with 800kg of regular first-cycle fermented mash and compact it, restoring the four-layer sealed structure; ③ Check the monitoring probes to ensure that the oxygen, Eh value, and temperature probes are working properly and are not damaged or displaced.

[0030] (5) Staged regulation of re-fermentation (70 days) ① The first 20 days (microbial community restart period): control the cellar temperature at 29-30℃, monitor the gas phase oxygen concentration ≤0.05%, and reduce the Eh value from -200mV to -220mV to promote the release of enzyme activity of the supplemented koji and accelerate starch degradation.

[0031] ②20-50 days (ester synthesis period): The fermentation pit temperature is raised to 32℃ (this temperature is the optimal temperature for the synthesis of ethyl hexanoate). The mash is tested every 10 days to ensure that the starch residue is reduced to 9-10wt%, the content of ethyl hexanoate precursor is increased by more than 50% compared with the first round, and the acidity is controlled at 4.2-4.3mmol / 10g.

[0032] ③ 50-70 days (stabilization period): The fermentation temperature drops to 30℃ to maintain stable microbial metabolism and avoid ester hydrolysis; at the end of 70 days of fermentation, the mash indicators are tested: moisture 64%, acidity 4.3mmol / 10g, starch 9.8wt%, hexanoic acid bacteria 25%, lactic acid bacteria 12%, completing the second round of fermentation; 5. Three-round fermentation: After the second round of fermentation, before the mash is transferred to the third-round fermentation pit, glucose-yeast extract (3:1) is added to the mash at a rate of 1.0%. After entering the pit, the mash is covered with pit mud and fermented for 70 days (total cycle 210 days). 6. Distillation: Atmospheric distillation is adopted, with a still temperature of 95-100℃, a distillation rate of 2L / min, and a steam pressure of 0.02MPa. The middle section of the wine, which is 65-75 vol%, is collected to obtain the raw wine.

[0033] Performance verification results:

[0034] Examples 1-2: Feeding Optimization Group Preparation steps: The only difference is that the amount of feed added in Example 1-1 is adjusted to 1.5% (added before the fermented mash is put into the pit after the third round of fermentation), and the rest of the steps are the same as in Example 1-1.

[0035] Performance verification results:

[0036] Example Group 2: Single-Factor Optimization Process Example 2-1: Optimization process for sterile airflow (oxygen volume concentration in the gas phase space of the pit is 0.8%) Preparation steps: 1. The steps for screening and mixing the mother mash are the same as in Example 1-1; 2. Fermentation in the pit: During the first 0-60 days of the three-round fermentation, the oxygen is consumed naturally (the oxygen concentration was 0.04% on the 60th day). During the later 60-70 days, sterile air is introduced and the oxygen concentration is controlled at 0.8% through bottom micropore aeration. The feed amount is 1.0% (added before entering the pit), and the other parameters remain unchanged.

[0037] Performance verification results:

[0038] Example 2-2: Optimization process for sterile airflow (oxygen volume concentration in the gas phase space of the pit is 1.0%) Preparation steps: The only difference is that the oxygen concentration in the later 60-70 days of Example 2-1 was adjusted to 1.0%, and the rest of the steps were exactly the same.

[0039] Performance verification results:

[0040] Examples 2-3: Optimization process for sterile airflow (oxygen volume concentration in the gas phase space of the pit is 1.2%) Preparation steps: The only difference is that the oxygen concentration in the later 60-70 days of Example 2-1 was adjusted to 1.2%, and the rest of the steps were exactly the same.

[0041] Performance verification results:

[0042] Examples 2-4: Optimization of Feeding Amount (1.0%) Preparation steps: 1. The steps for screening the mother mash and fermenting it in the pit are the same as in Example 1-1; 2. Before the fermented mash from the third round is put into the pit, 1.0% glucose and yeast extract (3:1) are added as feed, without additional sterile air control, and the other parameters remain unchanged.

[0043] Performance verification results:

[0044] Examples 2-5: Optimization of Feeding Amount (1.5%) Preparation steps: The only difference is that the feed amount in Examples 2-4 is adjusted to 1.5%, and the rest of the steps are exactly the same.

[0045] Performance verification results:

[0046] Examples 2-6: Optimization of koji dosage (5kg and 10kg) Preparation steps (taking 10kg of koji as an example): 1. The steps for screening the mother mash and fermenting it in the pit are the same as in Example 1-1; 2. When mixing the starter culture, crush 10kg of medium-high temperature starter culture and mix it with 800kg of mash. Use a double-spreading method (60% for the first time and 40% after mixing). For the 5kg starter culture group, reduce the amount of starter culture to 5kg. The mixing method is the same. The amount of supplementary material is 1.0% (added before entering the pit).

[0047] Performance verification results:

[0048] Examples 2-7: Processing of 5kg / 800kg of fermented mash with koji (fermentation starter) Preparation steps: When mixing the starter culture, crush 5 kg of medium-high temperature starter culture and mix it with 800 kg of mother lees. Sprinkle the starter culture in two batches (60% the first time and 40% the second time). The amount of supplementary material is 1.0% (added before entering the pit). The remaining steps are the same as in Example 1-1.

[0049] Performance verification results:

[0050] Examples 2-8: Processing of 10.0 kg of koji (fermented starter) per 800 kg of mash Preparation steps: When mixing the starter culture, crush 10.0 kg of medium-high temperature starter culture and mix it with 800 kg of mother lees. Sprinkle the starter culture in two batches, with a feed amount of 1.0% (added before entering the pit). The remaining steps are the same as in Example 1-1.

[0051] Performance verification results:

[0052] Example Group 3: Multi-factor synergistic optimization process Example 3-1: Combined process of 1.0% feed + 0.8% oxygen volume concentration in the gas phase space of the pit Preparation steps: 1. The steps for screening and mixing the mother mash are the same as in Example 1-1; 2. Before the fermented mash from the third round is put into the pit, add 1.0% glucose and yeast extract (3:1) as feed and mix well; 3. After entering the fermentation pit, fermentation lasts for 60-70 days. Sterile air is introduced to control the oxygen concentration at 0.8%. The remaining steps are exactly the same.

[0053] Performance verification results:

[0054] Example 3-2: Combined process of 1.0% feed material and 1.0% oxygen volume concentration in the gas phase space of the pit. Preparation steps: The only difference is that the oxygen concentration in the later 60-70 days of Example 3-1 was adjusted to 1.0%, and the rest of the steps were exactly the same.

[0055] Performance verification results:

[0056] Example 3-3: Combined process of 1.5% feed + 0.8% oxygen volume concentration in the gas phase space of the pit Preparation steps: The only difference is that the feed amount in Example 3-1 is adjusted to 1.5%, and the rest of the steps are exactly the same.

[0057] Performance verification results:

[0058] Examples 3-4: Combined process of 1.5% feed + 1.0% oxygen volume concentration in the gas phase space of the pit Preparation steps: The feed amount in Example 3-1 was adjusted to 1.5%, and the oxygen concentration was adjusted to 1.0% in the later 60-70 days. The remaining steps were completely the same.

[0059] Performance verification results:

[0060] Comparative group Comparative Example 1: Simple Two-Round Fermentation Process Preparation steps: Except for adjusting the fermentation cycle to 2 cycles (70 days per cycle, totaling 140 days, without a third fermentation stage), the other steps are completely consistent with Example 1-1.

[0061] Performance verification results:

[0062] Comparative Example 2: Bivariate Optimization of Two-Round Fermentation Process Preparation steps: Except for the fermentation cycle of 2 rounds (cumulative 140 days), the other steps are completely consistent with Example 3-1 (feeding 1.0% + oxygen concentration 0.8%).

[0063] Performance verification results:

[0064] Comparative Example 3: Double-round fermentation fed-batch culture medium 1.0% process Preparation steps: 1. Steps 1-2: Same as in Examples 2-4 (select 800 kg of 15% fermented mash from the bottom of the pit, add 7.5 kg of Daqu, ferment twice for 140 days, and screen to obtain mother mash with 63.03% moisture, 3.7 mmol / 10g acidity, 11.76% starch and 0.43% reducing sugar). 2. Step 3: Double-round fermentation (no third-round fermentation stage), add 1.0% feed before entering the pit, no additional oxygen content control, total fermentation cycle 140 days; 3. Step 4: The distillation parameters are the same as in Examples 2-4 (distillation rate 2L / min, steam pressure 0.02MPa), and 74.5% vol of raw wine is collected.

[0065] Performance verification results:

[0066] Comparative Example 4: 1.5% Feed-in Culture Medium in Two-Round Fermentation Process Preparation steps: 1. Steps 1-2: Same as in Examples 2-5 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 62.84% moisture, 4.13 mmol / 10g acidity, 12.93% starch and 0.53% reducing sugar). 2. Step 3: Double-round fermentation and continued fermentation, with 1.5% feed added before entering the pit, no oxygen content control, and a total fermentation cycle of 140 days; 3. Step 4: Distillation parameters are the same as in Examples 2-5, and 74.3% vol of raw spirit is collected.

[0067] Performance verification results:

[0068] Comparative Example 5: A process with a 0.8% oxygen volume concentration in the gas phase space of a double-stage fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Example 2-1 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 63.6% moisture, 4.51 mmol / 10g acidity, 11.83% starch and 0.62% reducing sugar). 2. Step 3: Double-round fermentation with sterile air introduced throughout (unlike the three-round fermentation which only introduces air for 60-70 days), oxygen concentration controlled at 0.8% through bottom micropore aeration, no feeding, total fermentation cycle 140 days; 3. Step 4: Distillation parameters are the same as in Example 2-1, and 74.2% vol of raw spirit is collected.

[0069] Performance verification results:

[0070] Comparative Example 6: A process with a 1.0% oxygen volume concentration in the gas phase space of a double-stage fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Example 2-2 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 63.75% moisture, 4.40 mmol / 10g acidity, 10.03% starch and 0.48% reducing sugar). 2. Step 3: Double-round fermentation continues, with sterile air introduced throughout (unlike the three-round fermentation which only introduces air for 60-70 days). The oxygen concentration is controlled at 1.0% through bottom micropore aeration, with no additional feeding. The total fermentation cycle is 140 days. 3. Step 4: Distillation parameters are the same as in Example 2-2, and 72.8% vol of raw spirit is collected.

[0071] Performance verification results:

[0072] Comparative Example 7: A process with a 1.2% oxygen volume concentration in the gas phase space of a double-stage fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Examples 2-3 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 63.68% moisture, 4.25 mmol / 10g acidity, 10.46% starch and 0.51% reducing sugar). 2. Step 3: Double-round fermentation with sterile air introduced throughout (unlike the three-round fermentation which only introduces air for 60-70 days), oxygen concentration controlled at 1.2% through bottom micropore aeration, no feeding, total fermentation cycle 140 days; 3. Step 4: Distillation parameters are the same as in Examples 2-3, and 71.3% vol of raw spirit is collected.

[0073] Performance verification results:

[0074] Comparative Example 8: Process with 1.0% feed added during double-stage fermentation + 0.8% oxygen volume concentration in the gas phase space of the fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Example 3-1 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 62.86% moisture, 3.68 mmol / 10g acidity, 12.38% starch and 0.48% reducing sugar). 2. Step 3: Double-round fermentation and continued fermentation. 1.0% feed is added before entering the fermentation pit and sterile air is circulated throughout the process (unlike the three-round fermentation which only circulates air for 60-70 days). The oxygen concentration is controlled at 0.8%, and the total fermentation cycle is 140 days. 3. Step 4: Distillation parameters are the same as in Example 3-1, and 74.1% vol of raw spirit is collected.

[0075] Performance verification results:

[0076] Comparative Example 9: Process with 1.5% feed added during double-stage fermentation + 0.8% oxygen volume concentration in the gas phase space of the fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Examples 3-3 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 62.11% moisture, 4.18 mmol / 10g acidity, 13.45% starch and 0.53% reducing sugar). 2. Step 3: Double-round fermentation and continued fermentation. 1.5% feed is added before entering the fermentation pit and sterile air is circulated throughout the process (unlike the three-round fermentation which only circulates air for 60-70 days). The oxygen concentration is controlled at 0.8%, and the total fermentation cycle is 140 days. 3. Step 4: Distillation parameters are the same as in Example 3-3, and 74.3% vol of raw spirit is collected.

[0077] Performance verification results:

[0078] Comparative Example 10: Process with 1.5% feed added during double-stage fermentation + 1.0% oxygen volume concentration in the gas phase space of the fermentation pit. Preparation steps: 1. Steps 1-2: Same as in Examples 3-4 (7.5 kg of Daqu mother mash, screened to obtain mother mash with 63.63% moisture, 4.45 mmol / 10g acidity, 11.49% starch and 0.61% reducing sugar). 2. Step 3: Double-round fermentation and continued fermentation. 1.5% feed is added before entering the fermentation pit and sterile air is circulated throughout the process (unlike the three-round fermentation which only circulates air for 60-70 days). The oxygen concentration is controlled at 1.0%, and the total fermentation cycle is 140 days. 3. Step 4: Distillation parameters are the same as in Examples 3-4, and 74.1% vol of raw spirit is collected.

[0079] Performance verification results:

[0080] Comparative Example 11: Double-round fermentation process with 5kg of starter culture and 0.8% oxygen volume concentration in the fermentation pit's gas phase space. Preparation steps: 1. Steps 1-2: Same as in Examples 2-6 (5kg of Daqu mother mash, screened to obtain mother mash with 63.88% moisture, 4.3mmol / 10g acidity, 10.3% starch and 0.45% reducing sugar). 2. Step 3: Double-round fermentation with sterile air throughout (unlike the three-round fermentation which only introduces air for 60-70 days), controlling the oxygen concentration at 0.8%, with no additional feeding, and a total fermentation cycle of 140 days; 3. Step 4: Distillation parameters are the same as in Examples 2-6, and 72.9% vol of raw spirit is collected.

[0081] Performance verification results:

[0082] Comparative Example 12: Double-stage fermentation process with 10 kg of starter culture and 0.8% oxygen volume concentration in the fermentation pit's gas phase space. Preparation steps: 1. Steps 1-2: Same as in Examples 2-6 (10kg of Daqu mother mash, screened to obtain mother mash with 64.54% moisture, 4.06mmol / 10g acidity, 9.99% starch and 0.46% reducing sugar). 2. Step 3: Double-round fermentation with sterile air throughout (unlike the three-round fermentation which only introduces air for 60-70 days), controlling the oxygen concentration at 0.8%, with no additional feeding, and a total fermentation cycle of 140 days; 3. Step 4: Distillation parameters are the same as in Examples 2-6, and 74.6% vol of raw spirit is collected.

[0083] Performance verification results:

[0084] The application completed a comprehensive comparative verification of the three-round fermentation process of strong-aroma baijiu and the traditional two-round fermentation process by setting up four core implementation examples (including 12 sub-schemes of three-round fermentation process) and 12 comparative examples of two-round fermentation. All experimental data directly cited the inventor's original test results. The experimental variables covered the amount of starter culture, the concentration of feed, the sterile air flow parameters and the synergistic combination of the whole process, realizing a complete demonstration of the relationship between process parameters and product quality.

[0085] From the perspective of physicochemical indicators of the fermented mash, the three-stage fermentation process significantly outperforms the two-stage fermentation process in terms of conversion efficiency: under the same amount of starter culture and basic fermentation conditions, the average residual starch content of the fermented mash from the three-stage fermentation process is 10.62%, which is 10.5% lower than the 11.87% of the two-stage fermentation process, and the average residual reducing sugar content is 0.38%, which is lower than the 0.48% of the two-stage fermentation process. Moreover, the three-stage fermentation process can stabilize the acidity of the fermented mash in the range of 3.42-4.44 mmol / 10g, avoiding the acidity imbalance problem under high feed or high sterile air flow conditions in the two-stage fermentation process (such as the acidity reaching 4.51 mmol / 10g in the 0.8% oxygen concentration group of the two-stage fermentation process). This indicates that the three-stage fermentation process makes fuller use of the fermented mash substrate and has stronger fermentation system stability.

[0086] At the core physicochemical level of the raw liquor, the three-round fermentation process significantly enhances the characteristic flavor compounds of strong-aroma baijiu: the ethyl hexanoate content in all groups of raw liquor from the three-round fermentation is above 910.26 mg / 100 mL, with the optimal group (1.0% feed + 0.8% oxygen concentration) reaching 1242.21 mg / 100 mL, an increase of 106.8% compared to the 600.75 mg / 100 mL in the two-round fermentation group with the same parameters; simultaneously, the three-round fermentation process can achieve the desired balance between ethyl hexanoate and... The balanced ratio of ethyl acetate, with an average hexyl-ethyl ratio of 1.52, is within the reasonable range (1.2-2.2) for high-quality strong-aroma baijiu. In contrast, the hexyl-ethyl ratio in most groups of the double-fermentation process is below 1.3, and in some high-sterile air groups it is even as low as 0.53, resulting in flavor imbalance. In addition, the fusel oil content of the raw liquor in the triple-fermentation process is an average of 15.7 mg / 100 mL, which is lower than the 21.3 mg / 100 mL in the double-fermentation process, effectively reducing the risk of bitterness and off-flavors in the raw liquor.

[0087] Analysis of sensory evaluation results shows that the overall sensory quality of the raw liquor produced by the three-round fermentation process is superior to that of the two-round fermentation process. The average sensory score of the raw liquor produced by the three-round fermentation process is 92.6 points, an increase of 1.1 points compared to the 91.6 points of the two-round fermentation process. Among them, the whole-process synergistic group (7.5kg of koji + 1.0% supplementary material + 0.8% oxygen concentration) scored 94 points, the highest in the group. Its evaluation reflects the excellent characteristics of "rich cellar aroma and ester aroma, full-bodied sweetness, and clean finish with a long aftertaste". In contrast, the two-round fermentation group with the same parameters only scored 91.5 points and had the defects of "heavy aftertaste with a strong fermented taste and a slightly astringent finish". In the koji optimization group, the three-round fermentation group with 10kg of koji and 0.8% oxygen concentration scored 93.1 points, an increase of 2.9 points compared to the 90.5 points of the two-round fermentation group with the same parameters. This compensates for the deficiency of the two-round fermentation process, which is prone to burnt taste due to the high amount of koji.

[0088] In summary, the three-stage fermentation process of this application, through the technical solution of physicochemical screening of mother mash and coordinated multi-parameter control, has achieved simultaneous improvement in mash conversion efficiency, original wine flavor quality and fermentation stability. Its technical effect is significantly improved compared with the traditional two-stage fermentation process, and the limitation range of each process parameter has been experimentally verified to be feasible.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A production method of a high-grade flavor liquor of Luzhou-flavor liquor, characterized in that, The method comprises the following steps: (1) double-round fermented mother distiller's grains preparation: taking the distiller's grains at the bottom of 15-20% height of the fermentation pit of Luzhou-flavor liquor, adding Luzhou-flavor liquor Daqu and treading into shape, laying clean steamed mature chaff on the top, carrying out double-round fermentation, each round cycle being 70±5 days, and the total cycle being 140 days, to obtain double-round fermented mother distiller's grains; (2) mother distiller's grains quality screening: detecting the acidity and starch residual amount of the double-round fermented mother distiller's grains, and screening qualified mother distiller's grains with acidity <4.5 mmol / 10 g of distiller's grains and starch residual amount <10 wt%; (3) three-round fermentation: transferring the qualified mother distiller's grains into a fermentation pit, the three-round fermented distiller's grains being on the top of one-round fermented distiller's grains, the whole pit being filled, the total fermentation cycle of three-round fermentation being 70±5 days, the total cycle of double-round fermentation and three-round fermentation being 210 days, the distiller's grains not being taken out during fermentation, and micro-oxygen regulation and feeding being carried out synchronously; (4) distillation: carrying out stepwise distillation on the three-round fermented distiller's grains, and collecting distillates with different alcohol contents; (5) hierarchical storage: transferring the middle section liquor into a ceramic jar for sealed storage, keeping the head section liquor for seasoning liquor, and using the tail section liquor for the next retort.

2. The production method according to claim 1, characterized by, The micro-oxygen regulation operation of step (3) comprises: not introducing sterile air in the early fermentation stage of 0-60 days, reducing the pit Eh to-200~-250 mV, and maintaining pH 3.5-4.2; continuously introducing sterile air in the late fermentation stage of 60-70 days, and controlling the oxygen volume concentration of the pit gas space to be 0.8-1.2%.

3. The production method according to claim 2, characterized by, The feeding operation of step (3) specifically comprises: adding a nutrient supplement to the qualified mother distiller's grains before the three-round fermented distiller's grains are put into the pit, the nutrient supplement being a mixture of glucose and yeast extract, the mass ratio of glucose to yeast extract being 3:1, and the addition amount being 1.0-1.5% of the mass of the qualified mother distiller's grains.

4. The production method according to claim 1, characterized by, The Daqu adding operation of step (1) comprises: the addition amount of Daqu being 0.625-1.25 kg / 100 kg of distiller's grains, the Daqu being added twice, the distiller's grains being tumbled after the first time of Daqu adding, the tumbling time being 5-8 min, and the distiller's grains being tamped into shape after the second time of Daqu adding.

5. The production method according to claim 4, characterized by, The mature chaff laying requirement of step (1) comprises: the chaff being treated by clean steaming for 30±5 min, the laying thickness being 1.8-2.2 cm, and the laying amount matching the surface area of the distiller's grains, the chaff only being used as a physical isolation layer.

6. The production method according to claim 1, characterized by, The stepwise distillation of step (4) specifically comprises: (a) head section liquor collection: collecting the distillate with alcohol content of 66-76 vol% at the standard temperature of 20℃, and the collection amount being 4-6% of the total distillation volume; (b) middle section liquor collection: collecting the distillate with alcohol content of 65-75 vol% at the standard temperature of 20℃, and the collection amount being 55-65% of the total distillation volume; (c) tail section liquor collection: collecting the distillate with alcohol content of 40-65 vol% at the standard temperature of 20℃, and the collection amount being 29-41% of the total distillation volume.

7. The production method according to claim 6, characterized by, The operation parameters of the stepwise distillation comprise: controlling the retort barrel temperature to be 95-100℃, controlling the distillation speed to be 2 L / min, adopting slow fire distillation mode, and maintaining the steam pressure at 0.02 MPa.

8. The production method according to claim 1, characterized by, The grading storage requirement of step (5) comprises: the middle section liquor is transferred into 200 L ceramic jar for sealed storage, the storage environment temperature is 20-24 ℃, the relative humidity is 65-75%, and the storage time is ≥ 3 years; the head section liquor is stored separately, and the tail section liquor is used for the next retort distillation.

9. The production method according to claim 1, characterized by, The fermentation pit specification of step (1) is: the pit mud thickness is 8-12 cm, and the pit mud pH value is 6.5-7.

5.

10. The production method according to claim 2, characterized by, The preparation method of the sterile air is: the compressed air is sequentially subjected to 0.1 μm precision activated carbon filtration, 254 nm wavelength ultraviolet sterilization, irradiation time 30±5 s, dew point ≤-40 ℃ drying treatment, and then introduced into the pit.

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