Green bean fragrant liquor brewing method based on ancient jar process

Abstract

The application discloses a kind of green bean fresh type Daqu liquor making methods based on ancient method ground jar process, comprising: shelling and crushing green bean and sorghum are mixed according to 10-15wt%:85-90wt%, high-temperature moistening, steaming and gelatinization are removed green bean impurities;Material is aired after adding 19wt%-23wt% low-temperature Daqu, into ancient method ground jar sealed fermentation 28 days, vertex temperature 28-32 ℃;Mature liquor mash is distilled for the first time and extracts 65%vol base liquor body, another fresh green bean is separately steamed and produces bean aroma steam, is introduced liquor mash and is re-distilled, and distillation speed is 2.5-3.5kg / min, and distillation temperature is 25-30 ℃;Base liquor is classified and stored in pottery jar.The application is strictly followed on the basis of fresh type Daqu liquor ancient method ground jar process, and the natural fusion of green bean fresh and Daqu fresh is realized by secondary series aroma distillation, and the obtained liquor body has traditional typical style and green bean fresh, and the process has strong landing nature.

Description

Technical Field

[0001] This invention relates to the field of baijiu brewing technology, specifically to a method for brewing mung bean-flavored daqu baijiu based on the traditional earthen vat solid-state fermentation process. Background Technology

[0002] Baijiu, one of the world's six major distilled spirits, boasts a long brewing history and profound cultural heritage in my country. Among them, the light-aroma type of baijiu, with its typical style of "pure aroma, mellow sweetness, natural harmony, and clean finish," is deeply loved by consumers. The traditional brewing process of light-aroma baijiu uses sorghum as the main raw material, with a low-temperature koji (fermentation starter) made from a mixture of barley and peas as the saccharification and fermentation agent. It employs a unique solid-state fermentation process in earthen vats, along with a clear steaming and distillation process, forming a pure flavor system distinct from strong-aroma and sauce-aroma baijiu. This traditional process has strict requirements for raw material selection, fermentation containers, fermentation cycle, and distillation operations. For example, ancient earthen vats are used as fermentation containers to isolate soil bacteria and maintain the purity of the fermentation system; a fermentation cycle of approximately 28 days is strictly followed; and during distillation, the process involves "observing the blooming of the liquor, cutting off the heads and tails, slow distillation, and maintaining a high temperature to finish the distillation," in order to control the quality and style of the liquor.

[0003] With the diversification of the consumer market, consumers' demand for innovative flavors in baijiu (Chinese liquor) is growing. Mung beans, as an agricultural product with both medicinal and edible properties, possess a unique aroma and health benefits such as clearing heat and relieving summer heat. Applying mung beans to baijiu brewing to develop new baijiu products with a distinctive mung bean aroma has broad market prospects.

[0004] However, existing mung bean brewing techniques have significant limitations. A common method involves directly mixing mung beans with other main brewing ingredients such as sorghum for co-fermentation and distillation. While this method is simple, during the 28-day solid-state fermentation in earthen vats, a large amount of the volatile aromatic substances in the mung beans are lost or transformed due to microbial metabolism, redox reactions, and heat generated during fermentation. This results in a weak mung bean flavor in the finished product, or even complete masking of the traditional grain aroma, making it difficult to achieve the desired flavor innovation.

[0005] Another method involves using liquid-state or solid-liquid processes to extract flavor components from mung beans using edible alcohol, or blending mung bean extract or fermented mung bean liquid with traditional base liquor as a flavoring agent. While these methods can retain some of the mung bean aroma, the resulting products often exhibit a "superficial" or "raw" flavor. The integration and harmony between the fresh mung bean aroma and the complex aroma of the liquor itself is poor, easily resulting in a sense of separation and an unnatural artificial fragrance, making it difficult to achieve the "clear, clean, and refreshing" quality of traditional Daqu-style light-aroma baijiu. Furthermore, these methods largely deviate from the core traditional solid-state fermentation process in earthen vats for light-aroma Daqu baijiu, resulting in deficiencies in process orthodoxy and product typicality.

[0006] Furthermore, mung beans themselves contain a certain amount of beany-smelling substances and proteins and fats that easily produce off-flavors. If they are directly involved in fermentation or cooking without special treatment, these unpleasant odor components may transfer to the liquor during the brewing process, ruining the original pure style of light-aroma baijiu. The traditional "high-temperature moistening" and "steaming and gelatinization" processes are key steps in removing off-flavors from the raw materials and ensuring the purity of the liquor in light-aroma baijiu. However, current technology lacks a scientific and systematic solution to integrate the pretreatment of mung beans into the above-mentioned core processes, making it difficult to effectively avoid the risk of off-flavors while introducing the flavor of mung beans. Summary of the Invention

[0007] In response to the problems of easy loss of mung bean aroma, awkward flavor integration, difficulty in removing off-flavors of mung beans, and disconnect between the process and the core requirements of traditional light-aroma baijiu in the existing technology, the present invention provides a method for brewing light-aroma baijiu based on the ancient earthen vat process.

[0008] This invention integrates the pretreatment of mung bean raw materials into the traditional process of high-temperature moistening and steaming gelatinization, strictly follows the 28-day solid-state fermentation standard, and innovatively introduces a secondary aroma distillation technology. While retaining the core standards of traditional distillation operations such as observing the aroma of the beans, removing the heads and tails, slow-fire distillation, and atmospheric finishing, it achieves a natural fusion of the aroma of mung beans and the aroma of Daqu (a type of Chinese liquor) at the molecular level. The resulting base liquor has both the typical style of Daqu aroma-type baijiu, which is clear, clean, and refreshing, and the natural fresh aroma of mung beans. Moreover, the process is entirely based on the existing production process and has strong practical applicability.

[0009] This invention includes the following technical solutions: A method for brewing mung bean-flavored Daqu Baijiu based on the traditional earthen vat brewing technique includes the following steps: S1: Pre-processing of mung bean raw materials The hulled and crushed mung beans are mixed with selected sorghum at a mass ratio of 10-15wt%: 85-90wt%. Hot water at a temperature of not less than 90℃ is added for high-temperature moistening, with the amount of water being 55-65wt% of the total mass of the mixed raw materials. The mixture is moistened for 20-25 minutes until there is no dry core or lumps. Then, it is put into a steamer for clear steaming and gelatinization. After the steam is fully released, the steaming time is 80-90 minutes to make the material cooked but not sticky, with no raw core, and the off-flavor of the mung beans completely removed. In the above scheme, high-temperature moistening is a key step in removing off-flavors from raw materials and allowing starch to fully absorb water and swell in the light-aroma baijiu. After mixing mung beans and sorghum, the mixture is moistened with hot water at a temperature of no less than 90℃. This high temperature effectively deactivates the lipoxygenase and other beany-producing enzymes in the mung beans, while also moderately denaturing the mung bean protein, reducing the dissolution of beany-flavor precursors. The moistened mixture is then steamed in a still, maintaining a steaming temperature of 80-90 minutes after the steam begins to rise. Sufficient steam penetration allows volatile off-flavor components in the mung beans to escape with the steam, while simultaneously completing deep gelatinization of the starch, providing a good enzymatic substrate for subsequent saccharification and fermentation.

[0010] S2: Solid-state fermentation in earthen vats Spread out the gelatinized material from step S1, add water at 35-45 wt% of the grain amount, cool to the temperature for entering the vat, add 19 wt%-23 wt% of the grain amount of light-aroma low-temperature Daqu and stir evenly. The low-temperature Daqu is made from 60 parts by weight of barley and 40 parts by weight of peas. Put the material into a traditional earthen vat and seal it for fermentation for 28 days. During the fermentation process, the peak temperature is controlled at 28-32℃ and the temperature at the vat outlet is 20-25℃ to obtain mature mash. In the above scheme, earthen vat fermentation is one of the core characteristics that distinguishes light-aroma baijiu from other aroma types. The earthen vats are made of fired clay and buried underground, providing excellent heat retention, moisture control, and micro-permeability, while also preventing direct invasion by soil-borne microorganisms. The fermentation cycle is strictly controlled at 28 days, matching the growth and metabolic patterns of microorganisms in the baijiu. In the early stage, yeast proliferates and starch saccharifies; in the middle stage, alcohol fermentation begins; and in the later stage, esters are produced and aroma develops. The peak temperature of 28-32℃ is a typical characteristic temperature for low-temperature fermentation of light-aroma baijiu. Temperatures above this range easily lead to excessive proliferation of acid-producing bacteria and spoilage of the mash; temperatures below this range result in incomplete fermentation and low alcohol yield. The low-temperature baijiu, formulated with 60wt% barley and 40wt% peas, provides abundant saccharifying and alcohol-producing enzymes. Simultaneously, the protein degradation in the peas produces various amino acids, providing precursors for the Maillard reaction in the later stages of fermentation, which generates characteristic aroma substances such as pyrazines.

[0011] S3: Secondary distillation of incense The mature mash obtained in step S2 is mixed with steamed rice husks and loaded into a still for the first distillation. The base liquor with an alcohol content of not less than 65% vol is extracted by slow distillation, observing the steam rise, and removing the heads and tails. Fresh mung beans are separately steamed in a still until the steam rises and then kept for 30 minutes to generate mung bean steam. The mung bean steam is then introduced into the mash through a still for a second distillation. During the second distillation, the distillation rate is controlled at 2.5-3.5 kg / min and the distillation temperature is 25-30℃ to obtain a base liquor with a mung bean aroma. In the above scheme: the first distillation follows the traditional slow-fire distillation and atmospheric tailing operation specifications. The slow fire allows the ethanol and aroma components in the mash to be distilled out steadily, avoiding the premature distillation of high-boiling-point impurities; cutting off the heads and tails effectively removes low-boiling-point irritating components such as methanol and aldehydes, as well as high-boiling-point fusel oils. The second aroma distillation is the core innovation of this invention: the steam generated by steaming fresh mung beans alone is rich in the characteristic aroma components of mung beans (including volatile flavor substances such as hexanal, nonanal, and 2-pentylfuran). This steam is introduced into the mash that has completed the first distillation and is redistilled under slow fire conditions. At this time, a certain amount of ethanol and water still remain in the mash. When the mung bean steam penetrates the mash layer, its aroma components undergo gas-to-gas mass transfer and intermolecular interactions with the ethanol steam in the mash, achieving a molecular-level fusion of the mung bean aroma and the aroma of the Daqu liquor, rather than a simple physical mixing. Meanwhile, controlling the distillation rate to 2.5-3.5 kg / min and the distillation temperature to 25-30℃ ensures that the aroma components of mung beans are fully condensed and recovered, avoiding aroma loss due to excessively fast distillation rate or excessively high temperature.

[0012] S4: Storage The base wine obtained in step S3 is graded and stored in earthenware jars for aging.

[0013] Principle: Freshly distilled base spirits contain a certain amount of low-boiling-point irritating components, resulting in a spicy and pungent taste. The microporous structure of the earthenware jar allows trace amounts of oxygen to slowly enter during aging, promoting the oxidation and esterification reactions of alcohols, aldehydes, and acids in the spirit, gradually making it mellow and smooth. Simultaneously, the metal ions in the earthenware jar catalyze the aging process, contributing to the further integration and refinement of the aromas of mung beans, grains, and yeast.

[0014] Furthermore, in step S1, the particle size of the dehulled and crushed mung beans is 4-8 segments, and the particle size of the crushed selected sorghum is 4-8 segments, wherein the proportion of fine powder passing through a 1.2mm sieve is 25-35wt%, and the content of whole grains does not exceed 0.3wt%.

[0015] In the above scheme: the particle size of mung beans and sorghum directly affects the moistening and gelatinization effect. A particle size of 4-8 lobes ensures that the material particles fully absorb water during moistening without excessive powdering and sticking; a fine powder content of 25-35 wt% provides an appropriate amount of starch contact surface, which is beneficial for gelatinization and enzymatic hydrolysis, but too much fine powder will lead to poor air permeability of the steamer and compressed steam during distillation; the whole particle content is controlled below 0.3 wt% to ensure gelatinization uniformity and avoid core formation.

[0016] Furthermore, in step S1, the temperature of the hot water used for the high-temperature moistening of the raw materials is 96-98℃, the amount of water added in summer is 65wt% of the total mass of the mixed raw materials, and the amount of water added in winter is 55wt% of the total mass of the mixed raw materials.

[0017] In the above scheme: hot water at 96-98℃ is close to boiling point, allowing it to quickly penetrate into the powdered particles, causing the starch granules to rapidly absorb water and swell. Simultaneously, the high temperature effectively deactivates the oxidase activity in the raw materials, reducing enzymatic browning and off-odors. In summer, when temperatures are high and evaporation is significant, appropriately increasing the water content to 65wt% can compensate for moisture loss. In winter, when temperatures are low and evaporation is low, reducing the water content to 55wt% can prevent excessive moisture content in the material, thus preventing rapid temperature rise and excessive acid production after entering the tank.

[0018] Furthermore, in step S2, the cylinder inlet temperature is 13-17°C in spring, autumn and winter, and 17-25°C in summer.

[0019] In the above scheme, the initial temperature upon entering the fermentation tank is a key parameter determining the fermentation temperature rise curve and peak temperature. Light-aroma baijiu requires a "slow initial temperature rise," and controlling the initial temperature at 13-17℃ allows the mash to gradually warm up in the early stages of fermentation, which is beneficial for yeast to gradually adapt and occupy its dominant ecological niche, inhibiting the early reproduction of bacteria and other miscellaneous microorganisms. In summer, when ambient temperatures are high and natural cooling capacity is limited, the temperature range can be appropriately relaxed to 17-25℃ to adapt to actual production conditions. However, it is still necessary to adjust the initial temperature upon entering the tank and strengthen ventilation to get as close to the ideal temperature range as possible.

[0020] Furthermore, in step S2, the sealed fermentation involves covering the cylinder opening with a plastic film, and then sealing it with a cylinder gasket and a stone slab or cement board.

[0021] Principle: Earthen vat fermentation requires a strictly anaerobic environment to promote alcoholic fermentation and inhibit the growth of aerobic acid-producing bacteria. The plastic film, with its excellent airtightness and flexibility, can be directly covered on the surface of the mash, isolating the vat from air. The sealing gasket acts as a buffer, providing insulation and further sealing. A stone slab or cement slab provides pressure, ensuring a tight seal between the plastic film and the vat opening. This three-layer sealing structure effectively maintains the anaerobic state within the vat, ensuring a stable fermentation process.

[0022] Furthermore, in step S3, the amount of steamed rice husks used is 14wt%-16wt% of the amount of grain fed, and the steamed rice husks are made by mixing rice husks and rice bran in a mass ratio of 7:3.

[0023] Principle: Rice husks, used as a distillation filler, primarily increase the looseness and permeability of the mash, preventing caking and steam compression during loading into the still. Steaming removes the bran-like odor from the rice husks, preventing off-flavors from entering the liquor. A 7:3 ratio of rice husks to rice bran provides structural support, while the finer particles of rice bran fill the gaps, resulting in more even steam distribution. Simultaneously, rice bran has a certain adsorption effect on high-boiling-point impurities, contributing to improved purity of the base liquor.

[0024] Furthermore, in step S3, during the first distillation, the loading of the still follows the operational requirements of two dry and one wet processes, and two small and one large steam processes, with a loading time of 45-55 minutes per still.

[0025] In the above scheme: "two dry and one wet" refers to spreading the material in three layers during loading, with the top and bottom layers relatively dry and the middle layer relatively moist, to create a reasonable steam resistance gradient; "two small and one large steam" refers to using small steam in the initial and middle stages of loading to prevent the material from being blown away, and using large steam in the later stages to ensure that the aroma components in the tail of the liquor are fully distilled out. A loading time of 45-55 minutes per still ensures that the material is evenly spread and appropriately compacted, creating conditions for stable distillation in the subsequent stages.

[0026] Furthermore, in step S3, during the secondary steaming process, the amount of fresh mung beans used is 5wt%-10wt% of the total grain feed.

[0027] In the above scheme, the amount of mung beans used in the secondary distillation directly affects the intensity of the mung bean aroma in the finished liquor. When the amount of mung beans is less than 5 wt%, the concentration of aroma components in the generated mung bean vapor is insufficient, and the mung bean characteristics of the finished liquor are not obvious; when the amount is more than 10 wt%, the mung bean flavor is too prominent, which may overpower the main flavor and disrupt the original flavor balance of light-aroma baijiu. The dosage range of 5 wt%-10 wt% has been verified through repeated experiments to achieve the best integration of the mung bean aroma and the aroma of daqu (a type of starter culture).

[0028] Furthermore, in step S4, the earthenware jar is stored for no less than 6 months.

[0029] Principle: The aging of base liquor in earthenware jars is a complex physicochemical process. During the aging process of more than six months, pungent components such as hydrogen sulfide and thiols in the new liquor gradually volatilize or transform; simultaneously, the hydrogen bonding between ethanol and water molecules increases, making the liquor smoother; aldehydes in the mung bean aroma undergo acetalization with alcohols, making the aroma more mellow and persistent. After at least six months of aging, the liquor reaches basic maturity and its style stabilizes.

[0030] In the above preparation method, the mung bean is any one or more of the following: mung bean, hairy mung bean, or parrot mung bean. Mung bean is preferred because it has a high starch content, moderate protein content, and relatively mild bean smell, making it more suitable for combination with the brewing process of light-aroma baijiu.

[0031] In the above preparation method, the still used for the secondary distillation in S3 is a traditional barrel still, and the introduction position of the mung bean steam is located at the bottom or lower middle part of the barrel, so that the steam penetrates the mash layer evenly from bottom to top.

[0032] In the above preparation method, the base liquor extracted during the first distillation in S3 preferably has an alcohol content of 65-68% vol. When extracting the liquor, the principle of "observing the foam and collecting the liquor" is followed. When the foam changes from "large clear foam" to "small clear foam", the middle section liquor is extracted and the extraction is stopped when the foam disappears.

[0033] The above preparation method also includes periodically monitoring the temperature, moisture and starch content of the mash during the S2 fermentation process. When the residual starch content of the mash drops to below 8 wt%, it is considered that the fermentation is complete and the mash can be removed from the fermentation tank for distillation.

[0034] A light-aroma type Daqu Baijiu prepared by the preparation method described in any of the above technical solutions has a harmonious blend of light aroma of mung beans and Daqu, a mellow and sweet taste, a pure and refreshing body, and a clean aftertaste, exhibiting the typical style of light-aroma Baijiu that is clear, clean, and refreshing.

[0035] The above-mentioned mung bean-flavored Daqu Baijiu is used in the preparation of liqueurs, fruit wines, or as a base for developing compound-flavored Baijiu products.

[0036] Compared with the prior art, the brewing method provided by the present invention has the following advantages: Employing a double-distillation technique, the aroma of mung beans is infused into the liquor through steam transfer during distillation, avoiding aroma loss caused by direct participation in long-term fermentation. The content of hexanal and nonanal, characteristic flavor components of mung beans, is increased by 7.7 times and 5.8 times, respectively, compared to the whole-fermentation method. The pretreatment of mung bean raw materials, including dehulling, high-temperature moistening, and steaming for 80-90 minutes, effectively removes the beany and off-flavors, reducing the fusel oil content of the base liquor by approximately 28% compared to the untreated group. Five consecutive batches of production trials show that the inter-batch RSD of alcohol content, total acid, total esters, and sensory scores are all less than 3%, indicating good process stability. The entire brewing process relies on existing light-aroma baijiu production equipment and technology system, requiring no major equipment modifications, making it suitable for large-scale promotion and application. Attached Figure Description

[0037] Figure 1 Comparison of the content (μg / L) of characteristic flavor components of mung beans in the liquor of this invention; Figure 2 This invention provides a comparison of sensory evaluation scores (total score) for baijiu (Chinese liquor). Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention. All raw materials used in the embodiments of this invention are commercially available.

[0039] The light-aroma type low-temperature koji used in this invention is a conventional commercially available product in the field. It is made from barley and peas in a 60:40 mass ratio through crushing, pressing, low-temperature cultivation, and storage, with the koji production temperature not exceeding 50°C. This type of koji adopts the traditional koji-making process of natural inoculation, without the addition of pure microbial strains. The microbial community in the koji comes from the natural enrichment of the koji-making environment, raw materials, and equipment.

[0040] Preferably, the light-aroma type low-temperature Daqu used in this invention is prepared by the following method: (1) Raw material ratio and crushing: Take 60 parts by weight of barley and 40 parts by weight of peas, mix them and crush them. The proportion of fine powder that passes through a 20-mesh sieve should be 20-30 wt%, and the proportion of coarse powder that does not pass through the sieve should be 70-80 wt%. (2) Adding water and mixing materials and pressing: Add water to the crushed raw materials to make the material moisture content reach 38-42wt%. After stirring evenly, press it into koji blanks. The koji blanks should be of uniform thickness and moderate tightness. (3) Entering the fermentation room: The fermented koji blanks are sent into the fermentation room and arranged at a spacing of 1-2cm. The fermentation process is divided into the mold stage (1-3 days after entering the room, product temperature 30-35℃), the damp fire stage (4-7 days, product temperature 35-45℃), the high fire stage (8-15 days, product temperature 45-50℃), and the post-fire stage (16-25 days, product temperature gradually drops back to 35-40℃). The product temperature shall not exceed 50℃ throughout the entire process. (4) Storage of koji: After the koji is cultivated, the koji blanks are taken out of the room and stored in a ventilated and dry place for 3-6 months until the moisture content drops to below 13wt%, and then mature light-fragrant low-temperature koji is obtained.

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0042] Example 1 A method for brewing mung bean-based light-aroma baijiu using traditional earthen vat brewing techniques includes the following steps (based on a grain input of 1000 kg): Raw material usage: 120kg of mung beans (after shelling and grinding) Sorghum: 880kg (to be crushed before use) Lightly aromatic low-temperature Daqu (fermented grain): 210kg (made from 60wt% barley and 40wt% peas, accounting for 21wt% of the total grain input). Rice husks: 150kg (mix rice husks and rice bran in a 7:3 mass ratio, steam before use, accounting for 15wt% of the grain input). Fresh mung beans (for secondary flavoring): 80 kg (8 wt% of total feed) Water content: 400 kg (40 wt% of grain feed) Preparation steps: S1: Pre-processing of mung bean raw materials After shelling, the mung beans are crushed into 4-8 pieces. Selected sorghum is also crushed into 4-8 pieces, with the fine powder (passing through a 1.2mm sieve) comprising 30wt% and whole grains comprising 0.2wt%. 120kg of the crushed mung beans and 880kg of sorghum are mixed evenly. 600kg of boiling water at 96℃ (for autumn production, accounting for 60wt% of the total mass of the mixed raw materials) is added for high-temperature moistening, moistening for 22 minutes until the material is free of dry centers and lumps. The moistened material is then loaded into a steamer for gelatinization, steaming for 85 minutes after the steam begins to rise. The material is cooked but not sticky, with no uncooked center, and the off-flavors of the mung beans are completely removed.

[0043] S2: Solid-state fermentation in earthen vats Spread the steamed and gelatinized material out to cool, add 400 kg of water, and let it cool to 15℃ (autumn) before placing it in the fermentation vat. Add 210 kg of light-aroma low-temperature Daqu (a type of starter culture) and mix well. Pack the material into traditional earthen vats, cover the vat opening with plastic film, and then seal it with a vat gasket and a stone slab. The fermentation period is 28 days. During fermentation, the temperature is monitored. The temperature is slowly increased in the early stage, reaching a peak temperature of 30℃ on the 12th day, and then slowly decreased in the later stage. The temperature at the end of the fermentation is 22℃, yielding mature mash.

[0044] S3: Secondary distillation of incense 150 kg of steamed rice husks were mixed evenly with the mature mash. The still was loaded following the "two dry, one wet; two small, one large steam" principle, with a loading time of 50 minutes. The first distillation was performed over a slow fire, observing the steam pattern and collecting the spirit, discarding the heads and tails to obtain a base spirit with an alcohol content of 65% vol. Separately, 80 kg of fresh mung beans were steamed separately, maintaining the steam for 30 minutes after it began to rise. This mung bean steam was then introduced into the mash through the bottom of the still for a second distillation at a rate of 3.0 kg / min, with the distillate temperature at 28℃, yielding a base spirit infused with the delicate aroma of mung beans.

[0045] S4: Storage The obtained base liquor is graded into three stages: head, middle, and tail, and stored in warehouses. The middle stage liquor (65% vol) is transferred to earthenware jars and aged for 8 months to obtain the finished product of mung bean aroma-type Daqu Baijiu.

[0046] Sensory evaluation of the finished product: It is colorless, clear and transparent, with a pure and elegant aroma of mung beans that blends harmoniously with the aroma of Daqu (a type of starter culture). It is smooth, sweet and mellow on the palate, with a clean body and a clean aftertaste.

[0047] Example 2 A method for brewing mung bean-based light-aroma baijiu using traditional earthen vat brewing techniques includes the following steps (based on a grain input of 1000 kg): Raw material usage: 100kg of mung beans (after shelling and grinding) 900 kg of sorghum Lightly aromatic low-temperature Daqu (fermented grain): 190 kg (19 wt% of grain input) Rice husks: 140 kg (rice husks and rice bran are mixed at a mass ratio of 7:3, accounting for 14 wt% of the grain input). Fresh mung beans (for secondary flavoring): 50 kg (5 wt% of total feed) Water content: 350 kg (35 wt% of grain feed) Preparation steps: S1: Pre-processing of mung bean raw materials The ground mung beans and sorghum have a particle size of 4-8 cloves, with fine powder accounting for 28 wt% and whole grains accounting for 0.2 wt%. 100 kg of mung beans and 900 kg of sorghum are mixed, and 650 kg of boiling water at 98℃ (for summer production, this accounts for 65 wt% of the total mass of the mixed raw materials) is added for high-temperature moistening for 25 minutes. The mixture is then steamed in a steamer until gelatinized, and the steaming time is 90 minutes after the steam begins to rise.

[0048] S2: Solid-state fermentation in earthen vats After the materials are spread out to cool, add 350 kg of water and let cool until the temperature reaches 20℃ (in summer). Add 190 kg of low-temperature Daqu (a type of starter culture) and mix well. Seal and ferment in traditional earthen vats for 28 days, with a peak temperature of 32℃ and an outlet temperature of 25℃.

[0049] S3: Secondary distillation of incense Mix in 140kg of steamed rice husks and steam for 45 minutes. First distill to extract 65% vol base liquor. Steam 50kg of fresh mung beans separately for 30 minutes, then introduce the mung bean steam into the mash for a second distillation at a rate of 2.5kg / min and a distillation temperature of 25℃.

[0050] S4: Storage After the base liquor is graded, the middle-grade liquor is aged in earthenware jars for 6 months.

[0051] Sensory evaluation of the finished product: It has a pure and refreshing aroma. The aroma of mung beans is slightly lighter than that of Example 1, but still clearly discernible. The wine is pure and refreshing, with a typical style.

[0052] Example 3 A method for brewing mung bean-based light-aroma baijiu using traditional earthen vat brewing techniques includes the following steps (based on a grain input of 1000 kg): Raw material usage: Mung beans: 150kg (after shelling and grinding) 850 kg of sorghum Lightly aromatic low-temperature Daqu (fermented grain): 230 kg (23 wt% of grain input) Rice husks: 160kg (rice husks and rice bran are mixed at a mass ratio of 7:3, accounting for 16wt% of the total grain input). Fresh mung beans (for secondary flavoring): 100 kg (10 wt% of total feed) Water content: 450 kg (45 wt% of grain feed) Preparation steps: S1: Pre-processing of mung bean raw materials The fine powder from the ground mung beans and sorghum comprised 32 wt% of the total powder, while the whole grain content was 0.1 wt%. 150 kg of mung beans and 850 kg of sorghum were mixed, and 550 kg of boiling water at 96℃ (for winter production, this amount comprised 55 wt% of the total mixed raw materials) was added for high-temperature moistening for 20 minutes. The mixture was then loaded into a steamer and steamed until gelatinized, and the steaming time was set for 80 minutes after the steam began to rise.

[0053] S2: Solid-state fermentation in earthen vats Add 450 kg of water and cool to 14°C (winter). Add 230 kg of low-temperature Daqu (fermentation starter) and mix well. Seal and ferment for 28 days, with a peak temperature of 28°C and an outlet temperature of 20°C.

[0054] S3: Secondary distillation of incense Mix in 160kg of steamed rice husks and steam for 55 minutes. First distillation to extract 65% vol base liquor. 100kg of fresh mung beans are steamed separately for 30 minutes, and the steam from the mung beans is introduced into the mash for a second distillation at a rate of 3.5kg / min and a distillation temperature of 30℃.

[0055] S4: Storage After the base liquor is graded, the middle-grade liquor is aged in earthenware jars for 12 months.

[0056] Sensory evaluation of the finished product: It has a pure and refreshing aroma, with a prominent mung bean aroma that blends well with the aroma of Daqu (a type of starter culture). After long-term aging, the liquor becomes more mellow and smooth with a full-bodied taste.

[0057] Comparative Example 1 The S3 secondary distillation step is omitted, and all mung beans participate in the fermentation.

[0058] Raw material usage: 200 kg of mung beans (directly participates in fermentation, accounting for 20 wt% of the grain input), 800 kg of sorghum, and the rest are the same as in Example 1.

[0059] Preparation steps: In S1, mung beans and sorghum are mixed, moistened, steamed, and then all of them are fermented in the earthen vat in S2. In S3, only a single distillation is performed (without secondary aroma transfer). The remaining steps are the same as in Example 1.

[0060] Results Analysis: The resulting base liquor had an extremely weak mung bean flavor, almost undetectable, with only a faint fermented bean aroma perceptible, failing to develop a clear mung bean fragrance. This indicates that direct participation of mung beans in the 28-day long fermentation process leads to a significant loss of mung bean aroma components.

[0061] Comparative Example 2 The S3 secondary distillation step is omitted, and mung bean extract is used instead for blending.

[0062] Raw material usage: S1-S2 are the same as in Example 1 (without adding mung beans), S3 is only a single distillation, and the resulting base liquor is blended with mung bean water extract concentrate.

[0063] Results Analysis: The resulting finished liquor exhibited a pronounced "floating" mung bean aroma. Upon tasting, the mung bean flavor was noticeably separated from the body of the liquor, with an unnatural sweetness and a slight raw bean taste in the aftertaste, resulting in poor overall harmony. This indicates that exogenous addition methods are insufficient to achieve a deep fusion of the fresh aroma of mung beans and the fresh aroma of Daqu (a type of starter culture).

[0064] Comparative Example 3 The high-temperature soaking and steaming gelatinization process of mixing mung beans and sorghum in S1 is omitted, and the mung beans are directly involved in fermentation after only simple washing.

[0065] Raw material dosage: Same as in Example 1, but the mung beans are not crushed, not mixed with sorghum for soaking and steaming, but simply washed, whole or coarsely crushed and then mixed with gelatinized sorghum in a vat for fermentation.

[0066] Results Analysis: The resulting base liquor had a distinct raw bean and grassy aroma, resulting in decreased purity and disrupting the typical "clear, clean, and refreshing" style of light-aroma baijiu. This indicates that without the "high-temperature soaking and gelatinization" process, the off-flavors could not be effectively removed from the mung beans.

[0067] Comparative Example 4 The amount of fresh mung beans used in the second distillation of the incense exceeded the upper limit.

[0068] Raw material usage: 200 kg of fresh mung beans (accounting for 20 wt% of the total grain input) for the second incense-making process, the rest is the same as in Example 1.

[0069] Results analysis: The mung bean flavor of the obtained base liquor was too prominent, which masked the main style of the light aroma of Daqu (a type of Chinese liquor), resulting in poor aroma balance and a style of finished liquor that deviated from the typical characteristics of light aroma baijiu.

[0070] Comparative Example 5 The methods of introducing steam from mung beans differ during the second distillation process.

[0071] Raw material usage: Same as in Example 1.

[0072] Preparation steps: In S3, instead of steaming the mung beans separately to generate steam, the fresh mung beans are directly mixed with the mash and then steamed a second time.

[0073] Results Analysis: The resulting base liquor exhibited a mixed aroma of raw green beans and boiled beans, indicating a decrease in aroma purity. Furthermore, the mung bean flavor was unevenly distributed throughout the liquor, with significant differences in flavor between the first and last sips. This suggests that the method of steaming mung beans separately to generate pure steam before introducing it into the mash is crucial for achieving a pure and uniformly integrated mung bean aroma.

[0074] Test Example 1 Detection of the content of characteristic flavor components in mung beans.

[0075] 1. Experimental objective: To verify the effect of double distillation on the retention of characteristic aromatic components of mung beans.

[0076] 2. Experimental methods: The finished wine samples prepared by Example 1, Example 2, Comparative Example 1 (full fermentation of mung beans), Comparative Example 2 (blending with mung bean extract), and Comparative Example 5 (direct mixing and re-steaming of mung beans) were selected, and the contents of hexanal, nonanal and 2-pentylfuran, characteristic flavor components of mung beans, were detected by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS).

[0077] Testing conditions: Extraction head: 50 / 30μm DVB / CAR / PDMS Extraction temperature: 60℃, extraction time: 40 min Chromatographic column: DB-WAX (60m × 0.25mm × 0.25μm) Temperature program: Hold at 40℃ for 3 minutes, then increase to 230℃ at a rate of 5℃ / min and hold for 10 minutes. Mass spectrometry scanning range: 35-450 amu, EI source 70 eV Quantification was performed using the external standard method, with each sample measured in triplicate. Results are expressed as mean ± standard deviation (μg / L).

[0078] 3. The results are shown in Table 1 and Figure 1 .

[0079] Table 1. Comparison of the content of characteristic flavor components of mung beans (μg / L).

[0080] As shown in Table 1, the content of characteristic flavor components in mung beans in Examples 1 and 2 is significantly higher than that in Comparative Example 1 (fully fermented mung beans), confirming that the double-distillation technique can effectively avoid the loss of mung bean aroma components during long-term fermentation. Although Comparative Example 2 has a higher content of flavor components, its flavor is "superficial" and poorly integrated according to sensory evaluation (see Test Example 2), indicating that a high content of chemical components alone does not equate to good sensory quality. In Comparative Example 5, because the mung beans were not steamed separately, some aroma components were masked or lost by off-flavors, and the content was significantly lower than in the examples. In summary, the double-distillation technique of the present invention has a significant advantage in preserving the purity of mung bean aroma.

[0081] Test Example 2 Sensory evaluation comparison experiment.

[0082] 1. Experimental objective: To comprehensively evaluate the sensory quality of the wines obtained from various processes and to verify the superiority of the method of this invention in terms of flavor fusion and typical style.

[0083] 2. Experimental methods: A sensory evaluation panel composed of seven national-level baijiu judges conducted a blind tasting of the finished baijiu from Examples 1, 2, 3, Comparative Examples 1, 2, 3, 4, and 5. Evaluation criteria included: color (10 points), aroma (30 points), taste (40 points), and style (20 points), for a total score of 100 points. The scoring criteria referenced the sensory requirements of GB / T10781.2-2006 "Light Aroma Baijiu," with the addition of "naturalness of mung bean aroma" as an additional descriptive item.

[0084] Each sample was randomly numbered, and the judges scored them independently, taking the average value and recording the main aroma descriptions.

[0085] 3. The experimental results are shown in Table 2 and Figure 2 .

[0086] Table 2 Comparison of Sensory Evaluation Scores

[0087] Example 1 received the highest total score, with its mung bean aroma described as elegant and natural, harmoniously blending with the aroma of Daqu (a type of starter culture), fully demonstrating the technical advantages of this invention. Comparative Example 3 received the lowest score, with a severe bean odor significantly affecting the quality of the liquor; while Comparative Example 2 received a slightly higher total score than Comparative Example 1, its aroma and flavor were noticeably separated. Examples 2 and 3 verified the effects of different mung bean addition ratios, both maintaining high scores. The results indicate that the "pretreatment + secondary aroma distillation" combined process of this invention is key to achieving a high-quality fusion of mung bean aroma and Daqu aroma.

[0088] Test Example 3 Comparison of physicochemical indicators and purity of base liquor.

[0089] 1. Experimental objective: To compare the main physicochemical indicators and fusel oil content of base wines obtained by different processes, and to verify the effect of the method of this invention on the purity of the wine.

[0090] 2. Experimental methods: Freshly distilled base liquor (without aging) produced in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were tested for alcohol content, total acidity, total esters, fusel oil (calculated as isobutanol + isoamyl alcohol), and methanol content according to GB / T10345-2007 "Analytical Methods for Baijiu". Each sample was measured in triplicate.

[0091] 3. The experimental results are shown in Table 3.

[0092] Table 3 Comparison of Physicochemical Indicators of Base Liquor

[0093] The total ester content of Example 1 (2.43 g / L) was higher than that of the comparative examples, indicating that the introduction of mung bean steam during the secondary distillation process may have promoted some esterification reactions or the synergistic extraction of aroma components. Comparative Example 3, due to the lack of steaming and gelatinization treatment of the mung beans, had significantly higher fusel oil content (0.67 g / L) and methanol content (0.18 g / L) than Example 1, indicating that off-flavor precursors in the raw materials were not effectively removed, affecting the purity of the spirit. The total acid, fusel oil, and methanol levels of Example 1 all met the superior grade standard of GB / T 10781.2-2006, indicating the best purity of the spirit.

[0094] Test Example 4 Evaluation of process stability and batch-to-batch consistency.

[0095] 1. Experimental objective: To verify the process stability and batch-to-batch consistency of the brewing method of this invention.

[0096] 2. Experimental methods: Using the process parameters of Example 1, five batches (numbered B1 to B5) of mung bean-aroma type Daqu Baijiu were produced continuously. Samples of the finished product from each batch were taken, and the alcohol content, total acidity, and total ester content were tested. A sensory evaluation panel then scored the samples (using the same standards as in Example 2). The relative standard deviation (RSD) of each indicator was calculated to assess batch-to-batch consistency.

[0097] 3. Experimental results: See Tables 4 and 5.

[0098] Table 4. Stability of Physicochemical Indicators for 5 Consecutive Batches

[0099] Table 5. Stability of Sensory Scores for 5 Consecutive Batches

[0100] The RSD of alcohol content was 0.35% for five consecutive batches of products, the RSD of total acid was 2.23%, the RSD of total esters was 1.12%, and the RSD of sensory score was 0.37%. The difference between batches of each indicator was less than 3%, indicating that the brewing method of the present invention has good process stability, strong batch consistency of products, and quality controllability for large-scale production.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention specification, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of protection of the present invention patent.

Claims

1. A method for brewing mung bean-flavored Daqu Baijiu based on the traditional earthen vat brewing technique, characterized in that, Includes the following steps: S1. Pre-treatment of mung bean raw materials: Mix the shelled and crushed mung beans with selected sorghum at a mass ratio of 10-15wt%: 85-90wt%, add hot water at a temperature not lower than 90℃ for high-temperature moistening, the amount of water added is 55-65wt% of the total mass of the mixed raw materials, moisten for 20-25 minutes until the material is free of dry core and lumps, then put it into a steamer for clear steaming and gelatinization, time 80-90 minutes after the steam is rounded, so that the material is cooked but not sticky, free of raw core, and the mung bean impurities are completely removed; S2. Solid-state fermentation in earthen vats: Spread out the gelatinized material from step S1, add water at 35-45 wt% of the grain input, cool to the vat temperature, add 19 wt%-23 wt% of the grain input of light-aroma low-temperature Daqu and stir evenly. The low-temperature Daqu is made of 60 parts by weight of barley and 40 parts by weight of peas. Put the material into an ancient earthen vat and seal it for fermentation for 28 days. During the fermentation process, the peak temperature is controlled at 28-32℃ and the vat temperature is 20-25℃ to obtain mature mash. S3. Secondary Distillation: The mature mash obtained in step S2 is mixed with steamed rice husks and loaded into a still for the first distillation. The base liquor with an alcohol content of not less than 65% vol is extracted by slow distillation, observing the steam rise, and removing the heads and tails. Fresh mung beans are separately steamed in a still until the steam rises and is kept for 30 minutes to generate mung bean steam. The mung bean steam is introduced into the mash through a still for a second distillation. During the second distillation, the distillation speed is controlled at 2.5-3.5 kg / min and the distillation temperature is 25-30℃ to obtain a base liquor with a mung bean aroma. S4. Aging: The base wine obtained in step S3 is graded and stored in earthenware jars for aging.

2. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S1, the particle size of the dehulled and crushed mung beans is 4-8 segments, and the particle size of the crushed selected sorghum is 4-8 segments. The proportion of fine powder passing through a 1.2mm sieve is 25-35wt%, and the content of whole grains does not exceed 0.3wt%.

3. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S1, the temperature of the hot water used for high-temperature moistening of the raw materials is 96-98℃, the amount of water added in summer is 65wt% of the total mass of the mixed raw materials, and the amount of water added in winter is 55wt% of the total mass of the mixed raw materials.

4. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S2, the inlet temperature is 13-17℃ in spring, autumn and winter, and 17-25℃ in summer.

5. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S2, the sealed fermentation is achieved by covering the jar opening with a plastic film, and then sealing it with a jar gasket and a stone slab or cement board.

6. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S2, temperature management during fermentation follows the principle of slow temperature increase in the early stage, sufficient temperature in the middle stage, and slow temperature decrease in the later stage.

7. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S3, the amount of steamed rice husks used is 14wt%-16wt% of the amount of grain fed, and the steamed rice husks are made by mixing rice husks and rice bran in a mass ratio of 7:

3.

8. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S3, during the first distillation, the loading of the still follows the operation requirements of two dry and one wet, and two small and one large steam, with a loading time of 45-55 minutes per still.

9. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S3, during the secondary steaming process, the amount of fresh mung beans used is 5wt%-10wt% of the total grain feed.

10. The method for brewing mung bean-flavored Daqu Baijiu based on the ancient earthen vat process according to claim 1, characterized in that, In step S4, the earthenware jar is stored for no less than 6 months.

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