Mung bean clear liquor and fermentation control method thereof

Abstract

This invention discloses a light-aroma baijiu made from mung beans and its fermentation control method, belonging to the field of baijiu brewing technology. The invention uses 80-85% red sorghum and 15-20% mung beans as raw materials. After dehulling and crushing, the mung beans are liquefied with low-temperature α-amylase (30-60 U / g) and mixed with sorghum. The mixture is then treated with phytase (10-20 U / g), moistened at high temperature, and steamed to gelatinize. After cooling, light-aroma low-temperature koji and ester-producing yeast are added to strengthen the koji. The mixture undergoes a two-stage variable-temperature fermentation in earthen vats: the first 7-10 days at 18-22℃, and the subsequent 18-21 days gradually increasing the temperature to 25-28℃, with a peak temperature ≤32℃ throughout the process, for a period of 28 days. The fermented mash is mixed with rice husks, loaded into stills, and distilled over a low flame. The distillate temperature is ≤25℃. 5-8% of the first and last sips are discarded, and the 65% vol middle section of the liquor is collected and aged in earthenware jars for more than 6 months. This invention constructs a three-stage fusel oil regulation system: "low-temperature liquefaction to control precursors, variable-temperature fermentation to inhibit formation, and slow-fire distillation to retain." The finished wine has a fusel oil content of ≤0.8g / L, a natural mung bean aroma, and a high level of comfort after drinking.

Description

Technical Field

[0001] This invention relates to the field of baijiu brewing technology, specifically to a mung bean-flavored baijiu and its fermentation control method. Background Technology

[0002] Light-aroma baijiu, with its "clear, pure, sweet, clean, and lingering" characteristics, is deeply loved by consumers. Traditional light-aroma baijiu is made from barley and peas using low-temperature koji (a type of starter culture), fermented with sorghum in earthen vats, and brewed through processes including steaming and distillation, slow distillation, storage, and blending. With increasing consumer demands for post-drinking comfort, the content of fusel oils (mainly isobutanol and isoamyl alcohol) in baijiu has become a key factor influencing post-drinking discomfort such as headaches and dry mouth. Fusel oils are byproducts of yeast metabolism during fermentation, generated from amino acid or sugar metabolism. Excessive levels can lead to headaches, dizziness, and other discomfort after drinking. Therefore, effectively reducing fusel oil content while maintaining the typical style of light-aroma baijiu has become a pressing technical problem to be solved in this field.

[0003] In existing technologies, there have been attempts to improve the quality of baijiu by optimizing the fermentation process or adding functional ingredients. For example, Chinese patent application CN106479832A discloses a light-aroma baijiu made with bran koji and its production method. It uses low-temperature koji, bran koji, ester-producing yeast, and yeast starter as saccharification and fermentation agents, and sorghum as the fermentation raw material. The baijiu is obtained through sealed fermentation and distillation, and the total ester content of the base liquor is improved. However, this method does not involve the active control of fusel oil content, and the fermentation cycle is relatively short (10-15 days), so the effect of inhibiting fusel oil formation is limited.

[0004] Chinese patent application CN120464458A discloses a formula and brewing method for using mung beans instead of peas to brew a light-aroma baijiu. In the koji-making stage, 5-10% of peas are partially replaced with mung beans, utilizing the antioxidant properties of flavonoids in mung beans to inhibit the formation of fusel oils. However, this method has the following shortcomings: First, mung beans are only added in small amounts during the koji-making stage and do not directly participate in fermentation as a raw material, thus limiting their effect on fusel oil regulation. Second, this method uses fermentation tanks instead of traditional earthen vats, resulting in higher fermentation temperatures (32-35℃ during the main fermentation period), increasing the risk of fusel oil formation. Third, this method does not treat the phytic acid in the raw materials; the inositol and phosphoric acid produced by the decomposition of phytic acid are important precursors for fusel oil formation. Fourth, only 2% of the distillate is removed during distillation, and the amount of tails removed is not specified, resulting in insufficient retention of already formed fusel oils. Fifth, this method does not specify the exact content of fusel oils in the finished baijiu, lacking quantitative verification of the technical effect.

[0005] Furthermore, in existing light-aroma baijiu production processes, raw material pretreatment typically involves only simple fermentation and steaming, without optimization for removing fusel oil precursors. When mung beans are used as fermentation raw materials, their lipoxygenases easily produce a beany odor, and direct addition leads to excessive protein decomposition, increasing amino acid nitrogen content and thus promoting fusel oil formation. Simultaneously, the inositol and phosphate produced by the decomposition of phytic acid during fermentation provide precursors for yeast metabolism, further exacerbating fusel oil formation.

[0006] Therefore, developing a fermentation control method for mung bean-flavored baijiu that can systematically and proactively reduce fusel oil content without altering the existing earthen vat fermentation process has significant practical implications and market value. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention proposes a mung bean-flavored baijiu and its fermentation control method. Specifically, it discloses a brewing method that uses red sorghum and mung beans as raw materials and actively reduces the fusel oil content through a three-stage fusel oil control system of "low-temperature liquefaction to control precursors, variable-temperature fermentation to inhibit formation, and slow-fire distillation to retain." This method aims to solve the technical problems of high fusel oil content and poor drinking comfort in existing baijiu, while also addressing the technical difficulties of excessive protein decomposition leading to increased fusel oil precursors and difficulty in removing the beany smell when mung beans are used directly as fermentation raw materials.

[0008] 2. Technical Solution The objective of this invention is achieved through the following technical solution.

[0009] A method for controlling the fermentation of a light-aroma mung bean-based baijiu, comprising the following steps: S1: Raw material pretreatment Take 80-85 wt% red sorghum and 15-20 wt% mung beans. After shelling and crushing the mung beans, add low-temperature α-amylase for liquefaction. The amount of low-temperature α-amylase added is 30-60 U per gram of dry mung bean raw material. Control the liquefaction temperature at 65-70℃ and liquefy for 30-60 minutes. After liquefaction, mix with red sorghum and add water at 55-65% for high-temperature moistening at 96℃. Then, steam and gelatinize, and maintain for 80 minutes after steaming. Add phytase during moistening and / or steaming and gelatinization. The amount of phytase added is 10-20 U per gram of raw material to decompose phytic acid in the raw material and reduce the formation of fusel oil precursors.

[0010] Preferably, the mung beans, after being dehulled and pulverized, have a particle size that meets the requirement of a 40-mesh sieve passing rate of ≥95%, to ensure sufficient exposure of starch and efficient enzymatic hydrolysis.

[0011] Preferably, the liquefaction temperature of the low-temperature α-amylase is 66-68℃, and the liquefaction time is 40-50 min.

[0012] Preferably, the amount of water added during the high-temperature sizing process is 58-62%, and the moisture content of the material after sizing is controlled at 52-56%.

[0013] Preferably, the phytase is added all at once at the beginning of the grazing process, or added in two parts during the grazing and steaming / gelatinization processes, with the amount added distributed proportionally.

[0014] S2: Spread out to cool and add yeast. Spread the gelatinized material out to cool to the temperature at which the hawthorn is placed in the vat (preferably controlled at 16-20℃). Add 19-23% of the grain weight of light-aroma low-temperature Daqu and 5-10% of the low-temperature Daqu weight of ester-producing yeast for strengthening. Mix well and then put it into a vat that has been cleaned and sterilized.

[0015] Preferably, the light-aroma low-temperature koji is prepared by the following method: using barley and peas as raw materials, with a barley to pea mass ratio of (3-6):(2-4), the process involves crushing, mixing with water, stepping on the koji, laying the koji flat, applying mold, drying the koji, moistening with heat, high heat, low heat, and nurturing the koji. The top heat temperature is controlled at 45-48℃, and the total koji-making cycle is 25-35 days. Specifically: 1) Grinding: The proportion of fine powder passing through a 20-mesh sieve is 20-30%; 2) Mixing with water: Add 50-55 kg of water per 100 kg of raw materials. The water temperature should be 14-16℃ in summer, 25-30℃ in spring, and 30-35℃ in winter. 3) Molding: Each piece of molten material uses 2.5-2.8kg, and the mold dimensions are 27-28cm inner length, 18-19cm inner width, and 5-6cm height; 4) Horizontal Curling: Dry rice husks are laid on the ground and reeds are used as dividers. The curling blanks are arranged in a triangular shape with a spacing of 3-4 cm between them; 5) Mold growth: Control the temperature of the fermentation room at 12-18℃, and raise the temperature of the fermented products to 38℃ after 72-80 hours; 6) Cooling and drying: Reduce the temperature of the product to 28-32℃ for 2-3 days, turning it over once a day; 7) Draining: When the product temperature reaches 36-42℃, drain the moisture 2-3 times a day; 8) High temperature: Maintain the product temperature at 45-46℃ for 7-8 days, not exceeding 48℃; 9) Post-heating: The product temperature is gradually reduced from 44℃ to 32-33℃ for 3-5 days; 10) Fermentation: Maintain an external temperature of 32℃ and a product temperature of 28-30℃ until the moisture in the core of the koji has evaporated completely; after leaving the room, it undergoes post-fermentation treatment.

[0016] Preferably, the ester-producing yeast-enhanced koji is prepared by the following method: using ester-producing yeast selected from *Hansenula anomala* and / or esterified *Saccharomyces cerevisiae* as the enhancing strain, and using a mixture of wheat bran and soybean meal as the solid culture medium, with a wheat bran to soybean meal mass ratio of 7:3-9:1, and processing it through the following steps: 1) Adjust the water content of the culture medium to 45-55%; 2) Sterilize at 121℃ for 20-30 minutes; 3) Inoculate with pure seed culture of the yeast, with an inoculation volume of 5-15% of the culture medium mass; 4) Expand the culture at 28-32℃ for 36-72 hours, turning the material over every 8-12 hours during the culture period; 5) After cultivation, dry at 40-50℃ until the moisture content is ≤10%, then pulverize and sieve to obtain the ester-producing yeast enhanced starter; The number of viable ester-producing yeasts in the enhanced broth is ≥1.0 × 10⁻⁶. 8 CFU / g.

[0017] S3: Two-stage variable temperature fermentation tank After being placed in the fermentation tank, the tank is sealed. The fermentation cycle is 28 days, and the peak temperature of the entire fermentation process is controlled below 32℃. During the first 7-10 days of fermentation, the temperature of the material in the tank is controlled at 18-22℃ to inhibit excessive yeast growth and reduce the formation of fusel oil. During the 18-21 days after fermentation, the temperature is gradually increased to 25-28℃ to promote ethanol production and esterification. After fermentation, the material is removed from the tank, and the temperature at which it is removed is controlled at 20-25℃.

[0018] Preferably, the transition conditions for the two-stage variable temperature fermentation are as follows: on the 8th-9th day of fermentation, when the material temperature reaches 24-26℃, the heating stage begins, with a heating rate of 1-2℃ per day, and the peak temperature is controlled at 28-30℃.

[0019] Preferably, the earthen vat is cleaned and sterilized with pepper water or hot alkaline water above 80°C before use, and the vat opening is sealed with wheat bran mud or food-grade plastic film.

[0020] S4: Mixing and loading into the steamer Mix the fermented mash with steamed rice husks, adding 18-22% of the mash's mass. Load the still using the "two dry, one wet, two small, one large steam" method: lightly spread the material at the bottom of the still, lightly spread and press the material in the middle of the still, and heavily press the material on the surface of the still. Control the steam pressure inside the still as follows: 0.02-0.04 MPa in the initial stage of loading, 0.04-0.06 MPa in the middle stage of loading, and 0.06-0.08 MPa in the final stage of loading.

[0021] Preferably, the steamed rice husks are pre-steamed separately for 30-40 minutes to remove any off-flavors.

[0022] S5: Slow-fired fractional distillation Control the temperature of the liquor to ≤25℃, the steam pressure to 0.10-0.20MPa, and the liquor flow rate to 2-4kg / min; increase the amount of head and tail to 5-8% of the total liquor output, of which the head is 2-3% and the tail is 3-5% of the total liquor output, in order to retain low-boiling-point fusel oil components and extract 65% vol of the middle liquor.

[0023] Preferably, the vapor phase temperature is strictly maintained at 78-95℃ during distillation, and the distillation ends when the alcohol content of the liquor drops to 15-20% vol.

[0024] S6: Tail processing The tails of the distillate are returned to the still for distillation, which continues until the alcohol content of the runoff drops to 15% vol - 20% vol, thus further retaining the fusel oils remaining in the tails.

[0025] S7: Aged The middle section of the wine is aged in earthenware jars for more than 6 months. During the aging period, the jars are rotated every 3-6 months. The aging temperature is controlled at 10-25℃ and the relative humidity at 65-80%.

[0026] Preferably, the ceramic jar is made of purple clay or traditional Chinese liquor ceramic jar, and the aging environment is kept ventilated, dark, and odorless.

[0027] S8: Stirring The aged wine is blended to obtain the finished wine.

[0028] Preferably, the blending process includes the following steps: grading and screening → physicochemical testing → small sample blending → large-scale blending → sensory evaluation → blending confirmation → volume reduction and slurry addition → filtration and turbidity removal → stabilization treatment → finished product filling.

[0029] The present invention also provides a mung bean-flavored baijiu, characterized in that it is prepared by any of the above-mentioned fermentation control methods, wherein the baijiu has a fusel oil content ≤0.8g / L (calculated as isobutanol and isoamyl alcohol) and a natural mung bean aroma.

[0030] Preferably, the liquor contains total esters ≥ 2.0 g / L, ethyl acetate ≥ 1.2 g / L, total acid ≥ 0.6 g / L, a liquor yield of 40-45% (65% vol), and methanol content ≤ 0.4 g / L.

[0031] Preferably, the content of isobutanol in the liquor is ≤0.3g / L and the content of isoamyl alcohol is ≤0.5g / L.

[0032] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the technical problem of high fusel oil content in baijiu (Chinese liquor) negatively impacting post-drinking comfort. It constructs a three-tiered control system—"low-temperature liquefaction to control precursors—variable-temperature fermentation to inhibit formation—slow-fire distillation to retain"—by focusing on three key aspects: raw material pretreatment, fermentation temperature control, and distillation operation. Test results show that in Examples 1-3 using the method of this invention, the fusel oil content in the finished liquor is 0.49-0.68 g / L, all below 0.8 g / L, with a yield of 41.9%-44.8% and total esters of 2.10-2.40 g / L. In contrast, Comparative Example 1 (omitting phytase) had 0.94 g / L fusel oil, Comparative Example 2 (constant-temperature fermentation) had 1.08 g / L fusel oil, and Comparative Example 3 (conventional head and tail removal) had 0.88 g / L fusel oil. Their sensory scores were also 16, 24, and 19 points lower than Example 1, respectively. Fermentation temperature comparison experiments further showed that the fusel oil concentration on day 28 in the gradient temperature increase mode (Mode D) of this invention was 376 mg / L, significantly lower than that in the constant temperature 28℃ mode (607 mg / L) and the two-stage constant temperature mode (507 mg / L). These data demonstrate that the three-level control system of this invention works synergistically, with each technical feature complementing the others rather than simply being additive, maintaining a high alcohol yield and ester content while reducing fusel oil. Furthermore, all control steps of this invention are implemented within existing earthen vat fermentation production processes, requiring no equipment modification and possessing good industrial applicability. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of a method for controlling the fermentation of mung bean-flavored baijiu according to the present invention. Figure 2 This is a comparison chart of fusel oil content in the finished wines of Examples 1-3 and Comparative Examples 1-5 of the present invention. The data corresponds to Table 1 of Test Example 1. Figure 3 This is a line graph comparing the sensory evaluation of the finished wines of Examples 1-3 and Comparative Examples 1-5 of the present invention. The data corresponds to Table 2 of Test Example 2. Figure 4 The figure shows the dynamic curves of fusel oil content with fermentation time under four fermentation temperature modes of the present invention. The data corresponds to Table 4 of Test Example 4. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only for illustrating the invention, but the implementation of the invention is not limited thereto. All equivalent substitutions or improvements made based on the technical concept of this invention should be included within the protection scope of this invention.

[0035] The present invention uses the following raw materials.

[0036] Example 1 This embodiment provides a method for controlling the fermentation of mung bean-flavored baijiu, and the specific steps are as follows: S1: Raw material pretreatment Take 850 kg (85 wt%) of red sorghum and 150 kg (15 wt%) of mung beans. Dehull and crush the mung beans, passing them through a 40-mesh sieve (96% passing rate). Add low-temperature α-amylase (enzyme activity 20000 U / g) to the mung bean powder at a rate of 45 U per gram of dry mung bean raw material, i.e., 2.25 kg of enzyme preparation per ton of mung beans. Control the liquefaction temperature at 67℃, the liquefaction time at 45 min, and the stirring speed at 30 rpm. After liquefaction, mix with the red sorghum, add 58% hot water at 96℃ (based on the total weight of the mixed raw materials), and moisten at high temperature for 30 min. Then, steam in a steamer to gelatinize, maintaining the steam level for 80 min after steaming. At the beginning of moistening, add phytase (enzyme activity 5000 U / g) at a rate of 15 U per gram of raw material, i.e., 3 kg of enzyme preparation per ton of mixed raw materials.

[0037] S2: Spread out to cool and add yeast. After gelatinizing, the material is spread out and cooled to 18℃. 21% of the grain weight of the light-aroma low-temperature Daqu (a type of starter culture) and 8% of the Daqu weight of ester-producing yeast for strengthening the starter culture are added, and the mixture is stirred evenly. The light-aroma low-temperature Daqu is prepared as follows: barley and peas are in a 6:4 mass ratio. The process involves crushing, mixing with water, pressing the starter culture, laying the starter culture flat, applying mold (15℃, increasing to 38℃ after 76 hours), drying the starter culture (30℃, 2.5 days), initial heating (38-42℃, dehumidification), high-temperature heating (46℃, 8 days), subsequent heating (34℃ to 32℃, 4 days), and conditioning the starter culture (30℃, 3 days), for a total cycle of 30 days. The ester-producing yeast-enhanced koji was prepared as follows: wheat bran to soybean meal mass ratio 8:2, moisture content 50%, sterilized at 121℃ for 25 min, inoculated with *Hansenula polymorpha* seed culture (inoculation amount 10%), cultured at 30℃ for 60 h, turned over every 10 h, dried at 45℃ to 8% moisture content, pulverized and sieved, with a viable count of 2.0 × 10⁻⁶. 8 CFU / g.

[0038] S3: Two-stage variable temperature fermentation tank The mixture is placed into a vat that has been cleaned with hot water, and the vat opening is sealed with food-grade plastic film. The fermentation cycle is 28 days. For the first 8 days, the material temperature inside the vat is controlled at 20℃; on the 9th day, the material temperature naturally rises to 25℃, and the temperature is then increased at a rate of 1.5℃ / day to 28℃, which is maintained until the 28th day. The peak temperature throughout the process is 28℃, and the outlet temperature is 23℃.

[0039] S4: Mixing and loading into the steamer Mix 20% steamed rice husks (pre-steamed for 35 minutes) into the fermented mash after it has been removed from the vat. Load the steamer according to the following method: "two dry, one wet, two small steam, one large steam": lightly sprinkle and spread the material at the bottom of the steamer, with a steam pressure of 0.03 MPa; lightly press and spread the material in the middle of the steamer, with a steam pressure of 0.05 MPa; and heavily press and compact the material on the surface of the steamer, with a steam pressure of 0.07 MPa.

[0040] S5: Slow-fired fractional distillation The distillation temperature was controlled at 23℃, the steam pressure at 0.15MPa, and the distillation rate at 3kg / min. The head portion was 2.5% of the total distillate, and the tail portion was 4.5%, totaling 7%. The middle section of the distillate was collected at 65% vol, and the tail portion was collected at an alcohol content of 18% vol.

[0041] S6: Tail processing The tail of the distillate is returned to the still for distillation, and distillation is stopped when the alcohol content of the runoff reaches 18% vol.

[0042] S7: Aged The middle section of the wine is poured into a purple clay pottery jar, sealed, and aged for 8 months in a pottery jar storage room at a temperature of 18℃ and a relative humidity of 70%, with the jar being rotated every 4 months during this period.

[0043] S8: Stirring The aged liquor was subjected to physicochemical testing in batches. A small amount of flavoring liquor was added to the base liquor for small-scale blending. After confirmation, the blending was scaled up and the alcohol content was reduced to 53% vol. After filtration through diatomaceous earth and stabilization for 20 days, the liquor was bottled to obtain the finished product.

[0044] Example 2 The difference between this embodiment and Example 1 lies in the raw material ratio, enzyme addition amount, and some process parameters, as detailed below: S1: Raw material pretreatment Take 800 kg (80 wt%) of red sorghum and 200 kg (20 wt%) of mung beans. Dehull and crush the mung beans, passing them through a 40-mesh sieve (97% passing rate). Add low-temperature α-amylase at 30 U / g mung beans, liquefying at 65℃ for 60 min. After liquefaction, mix with the sorghum, add 62% hot water at 96℃ to moisten the grits, and steam until gelatinized and retained for 80 min. Add phytase during moistening at 10 U / g of raw material.

[0045] S2: Spread out to cool and add yeast. The materials were spread out to cool to 16°C, and 19% of the grain weight of the light-aroma low-temperature Daqu (prepared as in Example 1) and 5% of the Daqu weight of the ester-producing yeast-enhanced Daqu (prepared as in Example 1) were added.

[0046] S3: Two-stage variable temperature fermentation tank For the first 10 days, the temperature was controlled at 18℃; on the 10th day, the product temperature was 24℃, and the temperature was increased at a rate of 1℃ / day to 26℃, which was maintained until the 28th day. The peak temperature was 26℃, and the discharge temperature was 20℃.

[0047] S4: Mixing and loading into the steamer The mash was mixed with 18% steamed rice husks, and the steam pressure in the steamer was initially 0.02 MPa, then 0.04 MPa, and finally 0.06 MPa.

[0048] S5: Slow-fired fractional distillation The distillation temperature was 20℃, the steam pressure was 0.10MPa, and the distillation rate was 2kg / min. 2% of the heads and 3% of the tails were removed, totaling 5%. 65% vol of the mid-section was collected, and 15% vol of the tails was collected.

[0049] The remaining steps (S6, S7, S8) are the same as in Example 1.

[0050] Example 3 The difference between this embodiment and Example 1 lies in the raw material ratio, enzyme addition amount, and some process parameters, as detailed below: S1: Raw material pretreatment Take 820 kg (82 wt%) of red sorghum and 180 kg (18 wt%) of mung beans. Dehull and grind the mung beans through a 40-mesh sieve (95% passing rate). Add low-temperature α-amylase at a dosage of 60 U / g mung beans, liquefy at 70℃ for 30 min. After liquefaction, mix with the sorghum, add 55% hot water at 96℃ to moisten the grits, and steam until gelatinized, maintaining this process for 80 min. Add phytase at the beginning of the steaming and gelatinization process at a dosage of 20 U / g of raw material.

[0051] S2: Spread out to cool and add yeast. The materials were spread out to cool to 20°C, and then 23% of the grain weight of a light-aroma low-temperature Daqu (barley:pea = 3:2, preparation process as in Example 1) and 10% of the Daqu weight of an ester-producing yeast-enhanced Daqu (wheat bran:soybean meal = 9:1, esterified brewing yeast, viable count 1.5 × 10⁻⁶) were added. 8 CFU / g).

[0052] S3: Two-stage variable temperature fermentation tank For the first 7 days, the temperature was controlled at 22℃; on the 8th day, the temperature was 26℃, and then increased to 30℃ at a rate of 2℃ / day, and maintained until the 28th day. The peak temperature was 30℃, and the discharge temperature was 25℃.

[0053] S4: Mixing and loading into the steamer The mash was mixed with 22% steamed rice husks, and the steam pressure during the initial loading of the still was 0.04 MPa, 0.06 MPa in the middle loading, and 0.08 MPa in the final loading.

[0054] S5: Slow-fired fractional distillation The distillation temperature was 25℃, the steam pressure was 0.20MPa, and the distillation rate was 4kg / min. 3% of the heads and 5% of the tails were removed, totaling 8%. 65% vol of the mid-section was collected, and 20% vol of the tails was collected.

[0055] The remaining steps (S6, S7, S8) are the same as in Example 1.

[0056] Comparative Example 1 The only difference between this comparative example and Example 1 is that phytase is not added in step S1; the other steps are exactly the same.

[0057] S1: Raw material pretreatment Take 850 kg of red sorghum and 150 kg of mung beans. After shelling and crushing the mung beans, add low-temperature α-amylase (45 U / g mung beans), liquefy at 67℃ for 45 min. After liquefaction, mix with sorghum, add 58% hot water at 96℃ to moisten the grits, steam until gelatinized, and maintain for 80 min. Do not add phytase.

[0058] S2 to S8 are the same as in Example 1.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that step S3 uses constant temperature fermentation, while the other steps are exactly the same.

[0060] S3: Constant Temperature Fermentation After the material is placed in the fermentation tank, the temperature of the material inside the tank is kept constant at 26℃. Fermentation lasts for 28 days, and the temperature at the outlet of the tank is 26℃.

[0061] S1, S2, S4 to S8 are the same as in Example 1.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that step S5 uses the conventional method of removing the beginning and end of the sample; the other steps are exactly the same.

[0063] S5: Conventional distillation The brewing temperature was controlled at 23℃, the steam pressure at 0.15MPa, and the brewing speed at 3kg / min. The initial distillation was 2% of the total brewed volume, and the final distillation was stopped when the alcohol content dropped below 45% vol (approximately 1% of the final volume was removed), totaling approximately 3% of the initial and final volume was removed. The 65% vol mid-section of the brew was collected.

[0064] S1 to S4 and S6 to S8 are the same as in Example 1.

[0065] Comparative Example 4 The difference between this comparative example and Example 1 is that the ester-producing yeast fortification koji is not added in step S2, while the other steps are exactly the same.

[0066] S2: Spread out to cool and add yeast. The materials are spread out to cool to 18°C, and only 21% of the grain weight of light-aroma low-temperature Daqu is added, without adding ester-producing yeast to strengthen the Daqu.

[0067] S1, S3 to S8 are the same as in Example 1.

[0068] Comparative Example 5 The difference between this comparative example and Example 1 is that the mung beans are not subjected to low-temperature α-amylase liquefaction treatment in step S1, while the other steps are exactly the same.

[0069] S1: Raw material pretreatment Take 850 kg of red sorghum and 150 kg of mung beans. After shelling and crushing the mung beans, do not add low-temperature α-amylase for liquefaction, and mix them directly with the red sorghum. Add 58% hot water at 96℃ to moisten the grits, and steam until gelatinized and rounded, then maintain for 80 minutes. Add 15 U / g of phytase to the raw materials during moistening.

[0070] S2 to S8 are the same as in Example 1.

[0071] Test case The following test examples demonstrate the physicochemical properties and sensory evaluation of the mung bean-aroma baijiu products prepared in Examples 1-3 and Comparative Examples 1-5. The physicochemical property testing methods followed the national standard GB / T 10345-2022 "Analytical Methods for Baijiu". Fusel oils (isobutanol and isoamyl alcohol) were determined by gas chromatography; total esters were determined by acid-base titration; ethyl acetate was determined by gas chromatography; methanol was determined by gas chromatography; and the yield was based on 65% vol of raw liquor. Sensory evaluation was conducted by a 10-person judging panel using a blind tasting method, with a maximum score of 100 points. The evaluation included post-drinking comfort (30 points, mainly evaluating headache, dry mouth, and sobering speed), aroma harmony (30 points, mainly evaluating the integration of mung bean aroma with the main aroma), body sweetness (20 points), and cleanliness (20 points). Each indicator was measured three times and the average value was taken.

[0072] Test Example 1 Determination of fusel oil content and main physicochemical indicators The finished wines from Examples 1-3 and Comparative Examples 1-5 were analyzed for fusel oil (isobutanol + isoamyl alcohol, g / L), total esters (g / L), ethyl acetate (g / L), total acid (g / L), methanol (g / L), and yield (%). The results are shown in Table 1 and 2. Figure 2 .

[0073] Table 1 Comparison of physicochemical properties between each embodiment and the comparative example

[0074] As shown in Table 1, the fusel oil content of Examples 1-3 ranged from 0.49 to 0.68 g / L, all ≤0.8 g / L, which was significantly lower than that of the comparative examples (0.70-1.08 g / L). Among them, Example 3 had the lowest fusel oil content (0.49 g / L), followed by Example 1 (0.55 g / L), while Example 2 had a relatively higher content (0.68 g / L). This trend is closely related to the process parameters of each embodiment: Example 3 used a higher proportion of mung beans (18%), a higher amount of α-amylase (60 U / g), and a higher amount of phytase (20 U / g), and the peak temperature of 30°C promoted the later esterification. At the same time, slow distillation with 8% head and tail removal resulted in the strongest synergistic effect of the three-stage regulation. The parameters of Example 1 were in the middle, and the effect was second best. Although Example 2 had the highest proportion of mung beans (20%), the amount of α-amylase added was low (30 U / g), the liquefaction temperature of 65°C was relatively low, and the fermentation peak temperature was only 26°C. This may have led to insufficient gelatinization of mung bean starch and incomplete protein decomposition, which instead increased the precursor of fusel oil. At the same time, insufficient esterification in the later stage of low-temperature fermentation meant that fusel oil could not be effectively converted or retained. Therefore, the fusel oil content was higher than that of Examples 1 and 3. This shows that a higher proportion of mung beans is not necessarily better. It must be combined with appropriate enzymatic hydrolysis conditions and fermentation temperature to achieve optimal regulation.

[0075] Test Example 2 Post-drinking comfort and sensory evaluation Sensory evaluations were conducted on the finished wines from Examples 1-3 and Comparative Examples 1-5, focusing on post-drinking comfort (headache, dry mouth, and sobering-up speed) and aroma harmony (the integration of mung bean aroma and Daqu aroma). The results are shown in Table 2 and... Figure 3 .

[0076] Table 2. Comparison of sensory scores between each embodiment and the comparative example (out of 100 points)

[0077] Sensory description record: Example 3 (Total score 91): The liquor is colorless, clear, and transparent, with a pure and elegant aroma of ethyl acetate and a natural and refreshing fragrance of mung beans, which are harmoniously blended. It is smooth, sweet, and mellow on the palate, with a gentle taste and no harshness. Ten minutes after drinking, there is no headache or dryness in the mouth; after 30 minutes, one feels completely comfortable, and the intoxication dissipates quickly. The sommelier's evaluation is "a mellowness within its elegance, with the aroma of mung beans and liquor perfectly integrated."

[0078] Example 1 (total score 85): The aroma is elegant, with a slightly milder mung bean fragrance than in Example 3, but without any beany taste; it is refreshing and clean on the palate with a noticeable sweet aftertaste; it leaves a slightly warm sensation after drinking, without causing headache or mild dryness in the mouth. Overall, it has good harmony.

[0079] Example 2 (total score 78): The aroma is rather weak, with a slight green bean fragrance and a hint of raw grain flavor; the body is somewhat thin, and while the aftertaste is acceptable, it lacks richness. This may be related to insufficient ester production due to the low fermentation temperature (peak 26℃).

[0080] Comparative Example 1 (Total Score 69): The aroma was rather simple, and the mung bean flavor was not prominent; a slight headache and noticeable dry mouth occurred 30 minutes after drinking.

[0081] Comparative Example 2 (Total Score 61): The aroma has a slightly dry and spicy feel, and it is slightly irritating on the palate; one hour after drinking, there is a noticeable headache and dry mouth, and some sommeliers reported that it "gets a headache quickly".

[0082] Comparative Example 3 (Total Score 66): The aroma of the wine is acceptable, but the aftertaste is slightly off-putting; the headache after drinking is moderate and the mouth is noticeably dry.

[0083] Comparative Example 4 (Total Score 67): The aroma is weak, the ester aroma is severely lacking, and the mung bean fragrance is almost imperceptible; the aftertaste is acceptable, but the body lacks complexity.

[0084] Comparative Example 5 (Total Score 67): It has a slight beany taste and the mung bean aroma is not pure; there is slight discomfort after drinking and the fusel oil content is too high.

[0085] Test Example 3 Effect of different head-and-tail removal ratios on fusel oil retention efficiency To verify the effect of increasing the head and tail removal ratio to 5-8% on the retention of fusel oil in this invention, based on the process of Example 1, comparative experiments were conducted in the S5 distillation step with head and tail removal ratios of 2% (head 1% + tail 1%), 3% (head 1.5% + tail 1.5%), 5% (head 2% + tail 3%), 7% (head 2.5% + tail 4.5%), and 9% (head 4% + tail 5%) (other steps were the same as in Example 1). The fusel oil content, total ester content, and alcohol yield of the finished wine (65% vol) at each ratio were measured, and the results are shown in Table 3.

[0086] Table 3. Effect of different head-and-tail removal ratios on fusel oil retention efficiency

[0087] As the percentage of heads and tails removed increased from 2% to 9%, the fusel oil content gradually decreased from 1.15 g / L to 0.42 g / L, a reduction of 63.5%, indicating that distillation retention was effective in removing fusel oils. However, total esters and ethyl acetate also decreased simultaneously, resulting in a lower alcohol yield. When the percentage of heads and tails removed reached 9%, although fusel oils decreased further, the loss of total esters was significant (from 2.45 g / L to 2.15 g / L), resulting in a bland spirit with insufficient aroma. This invention achieves the optimal balance between fusel oil control and aroma preservation by selecting a percentage of 5-8% (7% in Example 1).

[0088] Test Example 4 The effect of fermentation temperature mode on the dynamics of fusel oil formation Based on the raw materials and process of Example 1, four temperature modes were set in the S3 fermentation stage: Mode A (constant temperature 22℃), Mode B (constant temperature 28℃), Mode C (two-stage: 20℃ for the first 8 days → 28℃ for the next 20 days), and Mode D (the two-stage process of Example 1 of this invention: 20℃ for the first 8 days → increasing to 28℃ at 1.5℃ / day and maintaining it for the next 20 days). The fusel oil content (calculated as isobutanol + isoamyl alcohol, unit mg / L) in the mash was measured on days 7, 14, 21, and 28 of fermentation, and the final fusel oil content of the finished wine was recorded. The results are shown in Table 4. Figure 4 .

[0089] Table 4. Dynamic changes in fusel oil content (mg / L) during fermentation under different temperature conditions.

[0090] As can be seen from the data in Table 4, there are significant differences in the accumulation pattern of fusel oil during fermentation under different temperature modes. The fusel oil content of the four modes on day 28 is ranked as follows: Mode B (607 mg / L) > Mode C (507 mg / L) > Mode A (418 mg / L) > Mode D (376 mg / L). The fusel oil ranking of the finished wine is completely consistent, indicating that the accumulation trend of fusel oil during fermentation directly determines the fusel oil content of the final product.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 method for controlling the fermentation of a light-aroma mung bean-based baijiu, characterized in that, Includes the following steps: S1: Raw material pretreatment—Take 80-85wt% red sorghum and 15-20wt% mung beans. After the mung beans are dehulled and crushed to a 40-mesh sieve with a passing rate of ≥95%, add low-temperature α-amylase for liquefaction. The enzyme addition amount is 30-60U / g mung beans, the liquefaction temperature is 65-70℃, and the time is 30-60min. After liquefaction, mix with sorghum, add 55-65% water and moisten at 96℃, then steam and gelatinize until round steam is generated and held for 80min. Add phytase during moistening and / or steaming and gelatinization. The enzyme addition amount is 10-20U / g raw material. S2: Spreading and adding koji - Spread the material to a temperature of 16-20℃ before entering the vat, add 19-23% of light-aroma low-temperature koji and 5-10% of ester-producing yeast for strengthening koji, mix well and then put it into a ground vat that has been cleaned and sterilized. S3: Two-stage variable temperature earthen vat fermentation – sealed fermentation for 28 days, with peak temperature ≤32℃ throughout the process; for the first 7-10 days of fermentation, control the material temperature in the vat at 18-22℃; when the material temperature naturally rises to 24-26℃, enter the heating stage, gradually increasing the temperature to 25-28℃ at a rate of 1-2℃ / day, and maintaining it until the end of fermentation; the outlet temperature is 20-25℃. S4: Mixing and Loading the Steamer – Mix 18-22% steamed rice husks into the fermented mash after it has been removed from the vat, and load it into the steamer according to the "two dry and one wet, two small and one large steam" method. The steam pressure inside the steamer is controlled as follows: 0.02-0.04MPa in the initial stage, 0.04-0.06MPa in the middle stage, and 0.06-0.08MPa in the final stage. S5: Slow-fire fractional distillation - control the temperature of the distillate to ≤25℃, the steam pressure to 0.10-0.20MPa, and the distillate flow rate to 2-4kg / min; the amount of head-cutting is 2-3% of the total distillate, and the amount of tail-cutting is 3-5%, for a total of 5-8% of the head-cutting and tail-cutting amount, and obtain 65% vol of the middle section of the distillate. S6: Tail processing - The tail of the distillate is returned to the still and distilled until the alcohol content of the runoff is 15-20% vol; S7: Aging – The middle section of the wine is aged in earthenware jars for ≥6 months, with the jars being rotated every 3-6 months, at a temperature of 10-25℃ and a humidity of 65-80%; S8: Blending - Blending aged wine to obtain the finished wine.

2. The fermentation regulation method according to claim 1, characterized in that, The light-aroma type low-temperature Daqu in step S2 is prepared by the following method: using barley and peas as raw materials, with a mass ratio of (3-6):(2-4), and processed through the following steps: 1) Grinding: The proportion of fine powder passing through a 20-mesh sieve is 20-30%; 2) Mixing with water: Add 50-55 kg of water per 100 kg of raw materials. The water temperature should be 14-16℃ in summer, 25-30℃ in spring, and 30-35℃ in winter. 3) Molding: Each piece of molten material uses 2.5-2.8kg, and the mold dimensions are 27-28cm in inner length, 18-19cm in inner width, and 5-6cm in height; 4) Horizontal Curling: Dry rice husks are laid on the ground and reeds are used as dividers. The curling blanks are arranged in a triangular shape with a spacing of 3-4 cm between them; 5) Mold growth: The temperature in the koji room is 12-18℃, and the temperature of the koji in the koji room is raised to 38℃ after 72-80 hours; 6) Cooling and drying: Reduce the temperature of the product to 28-32℃ for 2-3 days, turning it over once a day; 7) Draining: When the product temperature reaches 36-42℃, drain the moisture 2-3 times a day; 8) High temperature: Maintain the product temperature at 45-46℃ for 7-8 days, not exceeding 48℃; 9) Post-heating: The product temperature is gradually reduced from 44℃ to 32-33℃ for 3-5 days; 10) Nurturing the koji: Maintain an external temperature of 32℃ and a product temperature of 28-30℃ until all moisture in the koji core has evaporated; After being taken out of the fermentation room, the koji undergoes a post-fermentation process, with the top firing temperature for koji making at 45-48℃, and the total cycle is 25-35 days.

3. The fermentation regulation method according to claim 1, characterized in that, The ester-producing yeast-enhanced starter in step S2 is prepared by the following method: using ester-producing yeast selected from *Hansenula polymorpha* and / or esterified *Saccharomyces cerevisiae* as the enhancing strain, and using a mixture of wheat bran and soybean meal at a mass ratio of 7:3-9:1 as the solid culture medium, and processing it through the following steps: 1) Adjust the water content of the culture medium to 45-55%; 2) Sterilize at 121℃ for 20-30 minutes; 3) Inoculate with pure seed solution, the inoculation amount being 5-15% of the culture medium mass; 4) Culture at 28-32℃ for 36-72 hours, turning the substrate every 8-12 hours; 5) Dry at 40-50℃ until moisture content ≤10%, then pulverize and sieve; The number of viable ester-producing yeasts in the enhanced broth is ≥1.0 × 10⁻⁶. 8 CFU / g.

4. The fermentation control method according to claim 1, characterized in that, In step S1, the liquefaction temperature of the low-temperature α-amylase is 66-68℃, and the time is 40-50 min; the water addition for high-temperature moistening is 58-62%, and the moisture content of the material after moistening is 52-56%.

5. The fermentation regulation method according to claim 1, characterized in that, In step S3, the transition conditions for the two-stage variable temperature fermentation are as follows: on the 8th-9th day of fermentation, when the material temperature reaches 24-26℃, the temperature begins to rise, and the peak temperature is controlled at 28-30℃.

6. The fermentation regulation method according to claim 1, characterized in that, In step S4, the steamer is loaded using a "two light and one heavy" method: lightly and evenly spread the material at the bottom of the steamer, lightly and evenly spread and lightly press the material in the middle of the steamer, and heavily press and compact the material on the surface of the steamer.

7. The fermentation regulation method according to claim 1, characterized in that, In step S5, the amount of head removed during slow-fire segmented distillation is 2-3%, and the amount of tail removed is 3-5%. The endpoint for tail distillation is when the alcohol content of the liquid is 15-20% vol.

8. The fermentation control method according to claim 1, characterized in that, In step S7, the earthenware jars are rotated every 3-6 months during the aging process, with a temperature of 10-25℃ and a relative humidity of 65-80%.

9. A type of light-aroma baijiu (Chinese white liquor) characterized by, Prepared by the fermentation control method according to any one of claims 1 to 8, the liquor has a fusel oil content ≤0.8g / L, wherein the isobutanol content ≤0.3g / L and the isoamyl alcohol content ≤0.5g / L, and has a natural mung bean aroma.

10. The mung bean-flavored baijiu according to claim 9, characterized in that, The liquor contains total esters ≥ 2.0 g / L, ethyl acetate ≥ 1.2 g / L, total acid ≥ 0.6 g / L, a liquor yield of 40-45% (65% vol), and methanol content ≤ 0.4 g / L.

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