A bran koji fragrant distiller's yeast and a preparation method thereof

Abstract

The application discloses bran-fermented fragrant wine starter and a preparation method thereof, and belongs to the technical field of brewing wine. The bran-fermented fragrant wine starter comprises the following components: a carrier, ester-producing active dry yeast, black-aspergillus bran-fermented powder, cellulase, pectinase, saccharifying enzyme, neutral protease and lipase. The preparation method comprises the following steps: S1, raw material pretreatment; S2, step-by-step premixing, wherein the carrier, saccharifying enzyme and cellulase are premixed at a temperature of less than or equal to 25 DEG C, the pectinase, neutral protease and lipase are premixed at a temperature of less than or equal to 20 DEG C, and then total mixing is performed; S3, gradient ultrafine grinding to 800-1000 meshes; S4, low-temperature vacuum drying to a water activity of less than or equal to 0.2; S5, low-temperature mixing of the dried product with ester-producing active dry yeast and black-aspergillus bran-fermented powder; and S6, vacuum packaging. The application designs differentiated protection measures for different heat-sensitive components, and maximally protects the activity of various heat-sensitive enzyme preparations and living microorganisms.

Description

Technical Field

[0001] This invention relates to the field of brewing technology, and more specifically, to a bran-based, light-aroma brewing starter and its preparation method. Background Technology

[0002] Wheat bran-based light-aroma baijiu is a type of baijiu produced by solid-state fermentation using wheat bran as the raw material, cultivated with pure mold to create wheat bran koji (fermentation starter), and sorghum and other grains as the fermentation agent. Wheat bran-based light-aroma baijiu is characterized by its short production cycle and high yield, and it forms the technological basis for well-known baijiu brands such as Erguotou.

[0003] Existing methods for preparing bran-based aromatic liquor starter typically involve weighing components such as saccharifying enzymes, active dry yeast, aroma-producing yeast, and bran starter in a specific ratio, then directly mixing, pulverizing, and packaging to obtain the finished product. For example, Chinese patent application CN102807937A discloses a method for preparing raw material liquor starter, which involves adding components such as saccharifying enzymes, α-amylase, cellulase, pectinase, acidic protease, Rhizopus koji, heat-resistant active dry yeast, aroma-producing yeast, and bran yeast to a dry powder mixer, mixing evenly, weighing, packaging, and sealing to obtain the finished product.

[0004] However, existing methods for preparing bran-based aromatic liquor starter have a long-neglected technical problem: bran-based aromatic liquor starter contains various heat-sensitive bioactive substances, including enzymes (such as saccharifying enzymes, cellulases, pectinases, and proteases) and live microorganisms (such as active dry yeast and Aspergillus niger spores). During conventional processing, especially in mixing, grinding, and drying stages, these substances are easily deactivated or experience a significant decrease in activity due to mechanical shearing forces, localized high temperatures, and high osmotic pressure. For example, during conventional ball milling or hammer milling, the local temperature of the material can rise to 40–60°C, leading to enzyme and protein denaturation; ordinary hot air drying temperatures are typically 40–80°C, which is particularly damaging to heat-sensitive enzymes and live bacteria; and friction between different components during simple mixing can also generate localized high temperatures.

[0005] This loss of enzyme and microbial activity leads to two main consequences: firstly, the core performance indicators of the starter culture, such as saccharification and fermentation power, cannot reach theoretical values, limiting starch conversion and alcohol yield; secondly, the activity of flavor-related enzyme systems (such as esterification enzymes) is impaired, resulting in insufficient generation of characteristic aroma components such as ethyl acetate in the liquor, leading to a thin and weak aroma. Furthermore, the insufficient or uncontrollable protein degradation capacity in existing starter cultures results in a higher amount of fusel oils, affecting post-drinking comfort.

[0006] Therefore, how to maximize the protection of the activity of heat-sensitive components and improve the overall performance of the yeast during the preparation of bran-based aromatic yeast is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to protect the activity of heat-sensitive enzyme preparations and live microorganisms through process means during the preparation of yeast, thereby improving the saccharification power, fermentation power and flavor generation ability of yeast.

[0008] Furthermore, the present invention also aims to address the problem of how to improve the overall performance of the yeast while protecting its activity, including increasing starch conversion rate, increasing the content of characteristic flavor substances of light aroma type, and reducing the amount of fusel oil generated.

[0009] To solve the above-mentioned technical problems, the present invention provides a method for preparing bran-based aromatic liquor starter, comprising the following steps:

[0010] S1. Raw material pretreatment: The carrier, cellulase, pectinase, saccharifying enzyme, neutral protease and lipase are sieved to remove impurities.

[0011] S2. Stepwise premixing: At an ambient temperature below 25°C, the sieved components are divided into two groups for premixing. The first group includes the carrier, saccharifying enzyme, and cellulase, and is premixed at ≤25°C. The second group includes pectinase, neutral protease, and lipase, and is premixed at ≤20°C. Then, the two premixed groups are mixed together at ≤20°C.

[0012] S3, stepped ultrafine grinding: The mixture obtained in S2 is first coarsely ground, and then subjected to airflow ultrafine grinding;

[0013] S4. Low-temperature vacuum drying: The ultrafine powder obtained in S3 is vacuum dried at a temperature below 30°C to reduce the water activity to below 0.2.

[0014] S5. Low-temperature mixing: The dried ultrafine powder obtained in S4 is mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at a temperature below 25°C.

[0015] S6. Packaging: Vacuum package the mixture obtained in S5 to obtain the finished product.

[0016] In a preferred embodiment, in S1, the cellulase and pectinase are sieved through a mesh size of 40-100, the saccharifying enzyme, neutral protease and lipase are sieved through a mesh size of 20-80, and the carrier is sieved through a mesh size of 20-80.

[0017] In a preferred embodiment, in S2, the premixing temperature of the second group is 3-8°C lower than that of the first group; the total mixing temperature is not higher than that of the second group; and the stirring speed of the mixing tank is 40-60 rpm.

[0018] In a preferred embodiment, in step S3, the material is first coarsely ground to 150-250 mesh, and then air-jet pulverized to 800-1000 mesh. The entire pulverization process is carried out at 15-25°C for 0.5-1.5 hours. During air-jet pulverization, the relative humidity in the pulverization chamber is controlled to be ≤30%.

[0019] In a preferred embodiment, the neutral protease has an enzyme activity of 50,000 to 100,000 U / g, and the lipase has an enzyme activity of 10,000 to 50,000 U / g.

[0020] In a preferred embodiment, in step S4, the vacuum drying time is 2 to 6 hours, and the vacuum degree is -0.08 to -0.1 MPa.

[0021] The present invention also provides a bran-based aromatic liquor starter, comprising the following components by mass percentage: 0%–12% carrier, 5%–15% ester-producing active dry yeast, 15%–25% Aspergillus niger bran starter powder, 10%–25% cellulase, 10%–20% pectinase, 5%–15% saccharifying enzyme, 3%–10% neutral protease, and 2%–8% lipase, with the sum of the mass percentages of each component being 100%.

[0022] In a preferred embodiment, the bran-based aromatic yeast is prepared by the above-described method, and the saccharification power of the yeast is ≥1000U / g.

[0023] In a preferred embodiment, when the bran-based aromatic yeast is used for brewing, the starch conversion rate is ≥95% under the following conditions: the amount of yeast added is 0.5% to 2% of the raw material mass, the fermentation temperature is 25 to 30°C, and the fermentation cycle is 3 to 5 days.

[0024] The present invention also provides the application of the above-mentioned bran-based light-aroma koji in the brewing of bran-based light-aroma baijiu.

[0025] The functions of each component in this invention are as follows:

[0026] (1) Carrier: Selected from one or more of wheat bran powder, rice husk powder, and corn cob powder, used to carry and dilute microorganisms and enzyme preparations, improve the flowability and dispersibility of the starter, and can be used by microorganisms as an auxiliary carbon source during fermentation. The carrier is not an essential component in the starter (as shown in Example 4), and its addition amount can be adjusted according to actual needs.

[0027] (2) Ester-producing active dry yeast (commonly known as aroma-producing yeast): It has the ability to esterify acids and alcohols, and promotes the generation of aroma-characteristic esters such as ethyl acetate.

[0028] (3) Aspergillus niger bran koji powder: Aspergillus niger is one of the most commonly used microorganisms in bran koji production. It can secrete a variety of enzyme systems such as α-amylase, saccharifying enzyme, acidic protease, pectinase, and cellulase. The natural enzyme system in Aspergillus niger bran koji powder works synergistically with exogenously added enzyme preparations to achieve efficient starch saccharification.

[0029] (4) Cellulase: dissolves cellulose in plant cell walls, destroys the skeletal structure of plant cell walls, releases intracellular starch and protein, and improves the availability of fermentable substrates.

[0030] (5) Pectinase: Degrades pectin substances in the middle layer of cell wall, reduces the viscosity of mash, and works with cellulase to break cell walls.

[0031] (6) Saccharifying enzyme: It is the core enzyme in starch saccharification, which converts starch into glucose.

[0032] (7) Neutral protease: It decomposes proteins into amino acids in a targeted manner, providing a high-quality nitrogen source for yeast fermentation and promoting yeast growth and metabolism. On the other hand, it effectively inhibits the formation of fusel oil by regulating the metabolic pathway of amino acids. Unlike the acidic protease used in the prior art, neutral protease has a milder and more selective protein degradation characteristic in the slightly acidic fermentation environment of the yeast.

[0033] (8) Lipase: hydrolyzes fat to generate free fatty acids, which then react with ethanol during fermentation to generate more fatty acid ethyl esters (such as ethyl acetate, ethyl hexanoate, ethyl butyrate, etc.), which synergistically enhance the aroma of esters with ester-producing active dry yeast.

[0034] The steps in the preparation method of this invention constitute a complete synergistic system:

[0035] (1) S1 Coarse sieving (20-100 mesh): Coarse sieving removes large particles of impurities, providing a reasonable starting point for subsequent cascade grinding. The reason for using a 20-100 mesh coarse sieve instead of a fine sieve is that step S3 will involve ultrafine grinding to 800-1000 mesh. If S1 has already ground the material to 400-600 mesh, then the subsequent "coarse grinding to 150-250 mesh" in S3 is physically and logically impossible. Therefore, S1 only performs coarse sieving to remove impurities, forming a reasonable particle size reduction gradient with the cascade grinding in S3 (20-100 mesh → 150-250 mesh → 800-1000 mesh).

[0036] (2) S2 Stepwise Premixing (Temperature Gradient 3-8℃): The heat-sensitive components (pectinase, neutral protease, and lipase, whose activity decays rapidly at higher temperatures) are premixed separately from the more stable components (carrier, saccharifying enzyme, and cellulase, which have relatively good thermal stability) at different temperatures to avoid the inactivation of heat-sensitive components due to local temperature increases during the mixing process. The premixing temperature of the second group is 3-8℃ lower than that of the first group, and the total mixing temperature is not higher than that of the second group. This temperature gradient design is based on a precise understanding of the differences in thermal stability of different enzyme components, achieving "precise temperature control" rather than "one-size-fits-all" low-temperature treatment, which protects the heat-sensitive components and avoids excessive cooling of all components, thus affecting the mixing efficiency.

[0037] (3) S3 stepped ultrafine grinding (800-1000 mesh, low temperature and low humidity): A stepped strategy is adopted, which first coarsely grinds (150-250 mesh) and then airflow ultrafine grinds (800-1000 mesh). Compared with one-step ultrafine grinding, coarse grinding first breaks the material into smaller particle sizes, reducing the processing load and grinding time of the ultrafine grinding stage, thereby reducing the time of mechanical damage to enzyme activity. Airflow ultrafine grinding uses the shear force of high-speed airflow and the collision force between particles to grind the material to the micron level (15-38 microns), which greatly increases the specific surface area of ​​enzyme preparation particles and significantly improves substrate accessibility, thereby improving saccharification efficiency and starch conversion rate. At the same time, the entire grinding process is carried out at a low temperature of 15-25℃, and the relative humidity in the grinding chamber is controlled to ≤30%, avoiding the dual damage to enzyme activity caused by high temperature and high humidity. High temperature accelerates enzyme protein denaturation, while high humidity causes ultrafine powder to absorb moisture and agglomerate, and enzyme activity is accelerated to decay in the presence of moisture.

[0038] (4) S4 Low-temperature vacuum drying (water activity ≤ 0.2): Vacuum drying is carried out at temperatures below 30°C. Compared with ordinary hot air drying (40–80°C), low-temperature vacuum drying fundamentally avoids the damage of heat-sensitive components to high temperatures. The water activity is reduced to below 0.2 because water activity is a key parameter affecting the stability of enzymes and microorganisms during storage. When the water activity is below 0.2, the metabolic activities of enzyme molecules and microbial cells are greatly inhibited, the three-dimensional conformation of enzymes is maintained, and microorganisms exist in a dormant state, thus achieving long-term stable storage of the yeast at room temperature.

[0039] (5) Post-addition of microorganisms in S5: Ester-producing active dry yeast (single-celled microorganisms, cell diameter approximately 5-10 micrometers) and Aspergillus niger bran powder (containing live hyphae and spores) are added only after S3 ultrafine grinding and S4 drying. This sequential arrangement avoids damage to the live microorganisms from mechanical shearing forces and collisions during the S3 ultrafine grinding process. The mechanical force generated by 800-1000 mesh ultrafine grinding is sufficient to destroy the cell walls and cell membranes of microorganisms, leading to leakage of contents and loss of activity. Post-addition of microorganisms fundamentally solves this contradiction, ensuring the survival rate and metabolic activity of microorganisms in the yeast.

[0040] The steps S1 to S6 described above are not simply superimposed, but constitute a complete "low-temperature protection process chain," namely, coarse sieving to remove impurities to ensure a reasonable particle size gradient (S1), step-by-step temperature control to avoid mixing damage (S2), low-temperature and low-humidity pulverization to avoid mechanical and damp-heat damage (S3), low-temperature vacuum drying to avoid thermal damage (S4), post-fermentation to avoid mechanical damage (S5), and vacuum packaging to isolate external moisture (S6). The process parameters of each step are designed to meet the protection requirements of specific heat-sensitive components. The steps work synergistically to achieve the efficient retention of various heat-sensitive bioactive substances in the yeast.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. This invention employs a complete low-temperature protection process chain consisting of "stepwise premixing (temperature gradient) + graded ultrafine pulverization (low temperature and low humidity) + low-temperature vacuum drying (water activity ≤ 0.2) + post-microbial addition," and designs differentiated protection measures for different heat-sensitive components, thereby maximizing the protection of the activity of various heat-sensitive enzyme preparations and live microorganisms.

[0043] 2. The activity of heat-sensitive components is effectively protected. In addition, the step-by-step ultra-fine grinding (800-1000 mesh) greatly increases the specific surface area of ​​enzyme preparation particles and significantly improves substrate accessibility. The starch conversion rate is ≥95%, the raw material utilization is more thorough, and the alcohol yield is significantly improved.

[0044] 3. The activity of the ester-producing active dry yeast is fully protected in the S5 post-addition step, and it works synergistically with lipase to enhance the aroma. The content of characteristic flavor substances such as ethyl acetate is significantly increased, resulting in a pure and fragrant baijiu with a long aftertaste.

[0045] 4. The activity of neutral protease is fully preserved in the low-temperature protection process of S1 to S4 of this invention, effectively regulating the protein degradation pathway. The content of fusel oil is ≤0.10g / L, which is more than 60% lower than the industry average (0.2-0.4g / L), and the post-drinking comfort is greatly improved.

[0046] 5. Low-temperature vacuum drying reduces the water activity to below 0.2. The product is packaged in vacuum aluminum foil bags, allowing for long-term stable storage at room temperature. It is moisture-proof, deterioration-proof, and adaptable to the storage and transportation requirements of high-temperature and high-humidity environments.

[0047] 6. The yeast of this invention is suitable for solid-state fermentation brewing of light-aroma baijiu made with bran yeast. It is not strict in terms of water quality and can ferment grains at room temperature or low temperature (above 16°C), which can save a lot of energy. Attached Figure Description

[0048] Figure 1 This is a flowchart of the preparation method of the bran-based aromatic wine starter in this invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0050] Example 1

[0051] 1. Raw material preparation

[0052] Weigh the following components by mass percentage:

[0053] Components mass percentage Carrier (wheat bran powder) 7% Ester-producing active dry yeast 12% Aspergillus niger bran koji powder 20% Cellulase 18% pectinase 15% Glucoamylase 10% neutral protease 10% Lipase 8%

[0054] The sum of the mass percentages of all components is 100%.

[0055] The activity of neutral protease was 80,000 U / g, and the activity of lipase was 30,000 U / g.

[0056] 2. Preparation steps

[0057] like Figure 1 As shown, the preparation method of this embodiment includes the following steps performed in sequence.

[0058] S1, Raw material pretreatment

[0059] Impurities were removed by sieving the carrier (wheat bran powder), cellulase, pectinase, saccharifying enzyme, neutral protease, and lipase. Cellulase and pectinase were sieved through a 60-mesh sieve; saccharifying enzyme, neutral protease, and lipase were sieved through a 50-mesh sieve; and the carrier was sieved through a 50-mesh sieve.

[0060] S2, Stepwise Premixing

[0061] At an ambient temperature below 25°C, the sieved components were divided into two groups for premixing:

[0062] Group 1: Carrier, saccharifying enzyme and cellulase, premixed at 25°C for 15 minutes;

[0063] Group 2: Pectinase, neutral protease and lipase, premixed at 20°C for 15 minutes.

[0064] The two premixes were then mixed at 20°C for 30 minutes at a stirring speed of 50 rpm.

[0065] S3, stepped ultrafine grinding

[0066] The mixture obtained from S2 was first coarsely pulverized to 200 mesh, and then subjected to airflow ultrafine pulverization to 900 mesh. The entire pulverization process was carried out at 20°C for 1 hour. The relative humidity inside the pulverization chamber was controlled at 25% during airflow ultrafine pulverization.

[0067] S4, Low-temperature vacuum drying

[0068] The ultrafine powder obtained from S3 was vacuum dried at 25°C to reduce the water activity to 0.18. The vacuum drying time was 4 hours, and the vacuum degree was -0.09 MPa.

[0069] S5, Low-Temperature Mixing

[0070] The dried ultrafine powder obtained from S4 was mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at 20°C for 20 minutes.

[0071] S6. Packaging

[0072] The mixture obtained from S5 is placed in an aluminum foil bag and vacuum-treated to obtain the finished product.

[0073] 3. Product performance testing

[0074] The saccharification power was tested according to the method specified in QB / T 4257-2011 "General Analytical Methods for Brewing Daqu".

[0075] The method for detecting starch conversion rate is as follows: using uncooked raw sorghum flour as raw material, fermentation is carried out at 1% of the raw material mass with yeast added at a fermentation temperature of 28℃ for 72 hours. After fermentation, samples of raw material before fermentation and samples of material after fermentation are taken. After defatting with petroleum ether and washing away soluble sugars with ethanol, the total starch content is determined by acid hydrolysis: accurately weigh 1-2g of sample, place it in an Erlenmeyer flask, add 100mL of 2% hydrochloric acid solution, connect a reflux condenser, and reflux in a boiling water bath for 3 hours to hydrolyze the starch into reducing monosaccharides. After cooling, the hydrolysate is neutralized to pH 6-7 with sodium hydroxide solution, and filtered after making up to volume. The reducing sugar content of the filtrate is determined by Fehling's reagent hot titration, using methylene blue as an indicator, and titrated until the blue color disappears as the endpoint. The starch content is calculated by multiplying the measured reducing sugar content by a conversion factor of 0.9. Starch conversion rate is calculated using the following formula: Starch conversion rate (%) = (Starch content before fermentation - Residual starch content after fermentation) / Starch content before fermentation × 100%.

[0076] The method for detecting fusel oil content refers to the gas chromatography method for the determination of "fusel oil" in GB / T 10345-2022 "Analytical Methods for Baijiu".

[0077] The method for detecting enzyme activity is as follows: refer to the method for determining total enzyme activity in QB / T 4257-2011 "General Analytical Methods for Brewing Daqu", where the enzyme activity is the total enzyme activity (calculated as saccharifying enzyme).

[0078] The properties of the bran-based aromatic liquor starter prepared in this embodiment were tested and are as follows:

[0079] Testing items Test results glycation power 1050U / g Starch conversion rate 96% Enzyme activity 46000U / g fusel oil content 0.08g / L

[0080] 4. Evaluation of Baijiu Quality

[0081] Using uncooked raw sorghum flour as raw material, solid-state fermentation was carried out using the bran-based, light-aroma koji prepared in this embodiment. The amount of koji added was 1% of the weight of the brewing raw materials. The fermentation temperature was 28℃, and the fermentation period was 25 days. The resulting baijiu, after tasting, was found to have a pure aroma, a pure and light fragrance, a rich cellar aroma, a long aftertaste, a sweet and refreshing taste, and a high level of comfort after drinking.

[0082] Example 2

[0083] 1. Raw material preparation

[0084] Weigh the following components by mass percentage:

[0085] Carrier (wheat bran powder) 11% Ester-producing active dry yeast 15% Aspergillus niger bran koji powder 18% Cellulase 20% pectinase 13% Glucoamylase 8% neutral protease 9% Lipase 6%

[0086] The sum of the mass percentages of all components is 100%.

[0087] The activity of neutral protease was 60,000 U / g, and the activity of lipase was 20,000 U / g.

[0088] 2. Preparation steps

[0089] like Figure 1 As shown, the preparation method of this embodiment includes the following steps performed in sequence.

[0090] S1, Raw material pretreatment

[0091] Impurities were removed by sieving the carrier (wheat bran powder), cellulase, pectinase, saccharifying enzyme, neutral protease, and lipase. Specifically, cellulase and pectinase were sieved through an 80-mesh sieve; saccharifying enzyme, neutral protease, and lipase were sieved through a 40-mesh sieve; and the carrier was sieved through a 40-mesh sieve.

[0092] S2, Stepwise Premixing

[0093] At an ambient temperature below 25°C, the sieved components were divided into two groups for premixing:

[0094] Group 1: Carrier, saccharifying enzyme and cellulase, premixed at 23°C for 12 minutes;

[0095] Group 2: Pectinase, neutral protease and lipase, premixed at 18°C ​​for 12 minutes.

[0096] The two premixes were then mixed at 18°C ​​for 25 minutes at a stirring speed of 55 rpm.

[0097] S3, stepped ultrafine grinding

[0098] The mixture obtained from S2 was first coarsely pulverized to 180 mesh, and then subjected to airflow ultrafine pulverization to 850 mesh. The entire pulverization process was carried out at 18°C ​​for 1.2 hours. The relative humidity inside the pulverization chamber was controlled at 28% during airflow ultrafine pulverization.

[0099] S4, Low-temperature vacuum drying

[0100] The ultrafine powder obtained from S3 was vacuum dried at 22℃ to reduce the water activity to 0.15. The vacuum drying time was 5 hours, and the vacuum degree was -0.085 MPa.

[0101] S5, Low-Temperature Mixing

[0102] The dried ultrafine powder obtained from S4 was mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at 18°C ​​for 15 minutes.

[0103] S6. Packaging

[0104] The mixture obtained from S5 is placed in an aluminum foil bag and vacuum-treated to obtain the finished product.

[0105] 3. Product performance testing

[0106] The performance was tested using the same method as in Example 1.

[0107] The test results are as follows:

[0108] glycation power 1030U / g Starch conversion rate 95% Enzyme activity 45000U / g fusel oil content 0.09g / L

[0109] Example 3

[0110] 1. Raw material preparation

[0111] Weigh the following components by mass percentage:

[0112] Carrier (wheat bran powder) 7% Ester-producing active dry yeast 10% Aspergillus niger bran koji powder 22% Cellulase 25% pectinase 12% Glucoamylase 12% neutral protease 8% Lipase 4%

[0113] The sum of the mass percentages of all components is 100%.

[0114] The activity of neutral protease was 100,000 U / g, and the activity of lipase was 40,000 U / g.

[0115] 2. Preparation steps

[0116] like Figure 1 As shown, the preparation method of this embodiment includes the following steps performed in sequence.

[0117] S1, Raw material pretreatment

[0118] Impurities were removed by sieving the carrier (wheat bran powder), cellulase, pectinase, saccharifying enzyme, neutral protease, and lipase. Cellulase and pectinase were sieved through a 40-mesh sieve; saccharifying enzyme, neutral protease, and lipase were sieved through a 30-mesh sieve; and the carrier was sieved through a 30-mesh sieve.

[0119] S2, Stepwise Premixing

[0120] At an ambient temperature below 25°C, the sieved components were divided into two groups for premixing:

[0121] Group 1: Carrier, saccharifying enzyme and cellulase, premixed at 20°C for 20 minutes;

[0122] Group 2: Pectinase, neutral protease and lipase, premixed at 17°C for 20 minutes.

[0123] The two premixes were then mixed together at 17°C for 20 minutes at a stirring speed of 45 rpm.

[0124] S3, stepped ultrafine grinding

[0125] The mixture obtained from S2 was first coarsely pulverized to 150 mesh, and then subjected to airflow ultrafine pulverization to 800 mesh. The entire pulverization process was carried out at 22°C for 1.5 hours. The relative humidity inside the pulverization chamber was controlled at 20% during airflow ultrafine pulverization.

[0126] S4, Low-temperature vacuum drying

[0127] The ultrafine powder obtained from S3 was vacuum dried at 28℃ to reduce the water activity to 0.19. The vacuum drying time was 6 hours, and the vacuum degree was -0.08 MPa.

[0128] S5, Low-Temperature Mixing

[0129] The dried ultrafine powder obtained from S4 was mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at 22°C for 25 minutes.

[0130] S6. Packaging

[0131] The mixture obtained from S5 is placed in an aluminum foil bag and vacuum-treated to obtain the finished product.

[0132] 3. Product performance testing

[0133] The performance was tested using the same method as in Example 1.

[0134] The test results are as follows:

[0135] glycation power 1010U / g Starch conversion rate 95% Enzyme activity 44000U / g fusel oil content 0.10g / L

[0136] Example 4

[0137] 1. Raw material preparation

[0138] Weigh the following components by mass percentage:

[0139] Ester-producing active dry yeast 8% Aspergillus niger bran koji powder 25% Cellulase 22% pectinase 18% Glucoamylase 14% neutral protease 7% Lipase 6%

[0140] The sum of the mass percentages of all components is 100%.

[0141] The activity of neutral protease was 70,000 U / g, and the activity of lipase was 45,000 U / g.

[0142] 2. Preparation steps

[0143] like Figure 1 As shown, the preparation method of this embodiment includes the following steps performed in sequence.

[0144] S1, Raw material pretreatment

[0145] Cellulase, pectinase, saccharifying enzyme, neutral protease, and lipase were sieved separately to remove impurities. Cellulase and pectinase were sieved through a 100-mesh sieve; saccharifying enzyme, neutral protease, and lipase were sieved through an 80-mesh sieve.

[0146] S2, Stepwise Premixing

[0147] At an ambient temperature below 25°C, the sieved components were divided into two groups for premixing:

[0148] Group 1: Saccharifying enzyme and cellulase, premixed at 24°C for 10 minutes;

[0149] Group 2: Pectinase, neutral protease and lipase, premixed at 16°C for 10 minutes.

[0150] The two premixes were then mixed together at 16°C for 40 minutes at a stirring speed of 60 rpm.

[0151] S3, stepped ultrafine grinding

[0152] The mixture obtained from S2 was first coarsely pulverized to 250 mesh, and then subjected to airflow ultrafine pulverization to 1000 mesh. The entire pulverization process was carried out at 15°C for 0.5 hours. The relative humidity inside the pulverization chamber was controlled at 30% during airflow ultrafine pulverization.

[0153] S4, Low-temperature vacuum drying

[0154] The ultrafine powder obtained from S3 was vacuum dried at 20℃ to reduce the water activity to 0.16. The vacuum drying time was 3 hours, and the vacuum degree was -0.095 MPa.

[0155] S5, Low-Temperature Mixing

[0156] The dried ultrafine powder obtained from S4 was mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at 16°C for 30 minutes.

[0157] S6. Packaging

[0158] The mixture obtained from S5 is placed in an aluminum foil bag and vacuum-treated to obtain the finished product.

[0159] 3. Product performance testing

[0160] The performance was tested using the same method as in Example 1.

[0161] The test results are as follows:

[0162] glycation power 1080U / g Starch conversion rate 97% Enzyme activity 47000U / g fusel oil content 0.07g / L

[0163] Comparative Example 1

[0164] A conventional method in the existing technology was used to prepare a bran-based, aromatic wine starter.

[0165] 1. Raw material preparation

[0166] Weigh the following components by weight percentage: 35% saccharifying enzyme (100,000 U / g), 1% α-amylase (20,000 U / g), 5% cellulase (20,000 U / g), 8% pectinase (20,000 U / g), 3% acidic protease (50,000 U / g), 15% Rhizopus moniliformis (≥10,000 U / g), 5% thermostable active dry yeast (≥30 billion / g), 5% ester-producing active dry yeast (≥3 billion / g), and 23% bran yeast (≥30 billion / g).

[0167] 2. Preparation steps

[0168] After weighing the above components according to the proportions, add them directly to the dry powder mixer, mix them evenly at room temperature, weigh, package, and seal to obtain the finished product.

[0169] 3. Product performance testing

[0170] The performance was tested using the same method as in Example 1.

[0171] The test results are as follows:

[0172] Testing items Test results glycation power 582U / g Starch conversion rate 82% Enzyme activity 35000U / g fusel oil content 0.28g / L

[0173] Comparative Example 2

[0174] 1. Raw material preparation

[0175] The same raw material ratio as in Example 1 was used (carrier (wheat bran powder) 7%, ester-producing active dry yeast 12%, Aspergillus niger wheat bran powder 20%, cellulase 18%, pectinase 15%, saccharifying enzyme 10%, neutral protease 10%, lipase 8%).

[0176] 2. Preparation steps

[0177] Weigh all the above components according to the proportions, add them all together into a dry powder mixer, mix them evenly at room temperature (without stepwise premixing, stepwise ultrafine grinding, or low-temperature vacuum drying), then directly grind them to 80 mesh and package them to obtain the finished product.

[0178] 3. Product performance testing

[0179] The performance was tested using the same method as in Example 1.

[0180] The test results are as follows:

[0181] glycation power 650U / g Starch conversion rate 85% Enzyme activity 38000U / g fusel oil content 0.22g / L

[0182] Performance comparison and mechanism analysis of the examples and comparative examples

[0183] 1. Performance Comparison

[0184] detection indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Glycochemical power (U / g) 1050 1030 1010 1080 582 650 Starch conversion rate (%) 96 95 95 97 82 85 Enzyme activity (U / g) 46000 45000 44000 47000 35000 38000 Fusel oil content (g / L) 0.08 0.09 0.10 0.07 0.28 0.22

[0185] 2. Mechanism Analysis

[0186] The comparison results above show that the saccharification power, starch conversion rate, and enzyme activity of Examples 1-4 of the present invention are significantly better than those of Comparative Examples 1 and 2, while the fusel oil content is significantly lower than that of Comparative Examples 1 and 2. The reason for this is the synergistic effect of the various process features of the present invention, as follows:

[0187] (1) Temperature gradient effect of stepwise premixing

[0188] In Comparative Example 2, all components were mixed at room temperature in a single step, resulting in a loss of activity in the heat-sensitive components (pectinase, neutral protease, and lipase) due to localized frictional heating during mixing. In contrast, this invention premixes the heat-sensitive components separately from the more stable components, and the second group is 3–8°C lower than the first group, achieving precise temperature control. In Example 4, the temperature difference reached 8°C (24°C for the first group and 16°C for the second group), and its saccharification power (1080 U / g) and starch conversion rate (97%) were the highest among all examples, indicating that the temperature gradient has a significant impact on enzyme activity retention.

[0189] (2) Specific surface area effect of stepped ultrafine grinding

[0190] Comparative Example 2, pulverized only to 80 mesh, had relatively large particles, limiting the contact area between the enzyme and the substrate. This invention employs a tiered strategy of 150-250 mesh coarse powder followed by 800-1000 mesh ultrafine powder, dramatically increasing the specific surface area of ​​the enzyme preparation particles and significantly improving substrate accessibility. The starch conversion rates of Examples 1-4 (95%-97%) were significantly higher than those of Comparative Example 2 (85%), confirming the contribution of ultrafine pulverization to improving raw material utilization.

[0191] (3) Water activity control effect of low temperature vacuum drying

[0192] Comparative Example 2, which did not undergo vacuum drying, had a high water activity, leading to a continuous decline in enzyme activity during storage and transportation. This invention reduces the water activity to below 0.2, allowing the enzyme molecules and microorganisms to exist in a dormant / stable state. The enzyme activities of Examples 1-4 (44000-47000 U / g) were significantly better than those of Comparative Example 2 (38000 U / g), demonstrating the positive effect of low water activity on the long-term maintenance of enzyme activity.

[0193] (4) The protective effect of post-addition of microorganisms

[0194] In Comparative Example 2, the ester-producing active dry yeast and Aspergillus niger bran koji powder were pulverized together with the enzyme preparation, resulting in mechanical damage to the living microorganisms. In this invention, the microorganisms are added only after ultra-fine pulverization and drying, avoiding mechanical damage to the cell walls / membranes. The fusel oil content in Examples 1-4 (0.07-0.10 g / L) was significantly lower than that in Comparative Example 1 (0.28 g / L) and Comparative Example 2 (0.22 g / L), indicating that the activity of the ester-producing active dry yeast and Aspergillus niger bran koji powder was fully protected, effectively regulating the fermentation metabolic pathway and inhibiting the formation of fusel oil.

[0195] In summary, the "stepwise premixing (temperature gradient) + graded ultrafine pulverization (low temperature and low humidity) + low temperature vacuum drying (water activity ≤ 0.2) + post-microbial addition" process of this invention constitutes a complete low-temperature protection process chain. Each step works in concert, synergistically enhancing the effects of these steps, thereby achieving efficient retention of various heat-sensitive bioactive substances in the yeast and a significant improvement in the overall performance of the yeast. Comparative Example 2 uses the same raw material ratio as Example 1 but omits the aforementioned process features; its performance indicators are all significantly lower than those of Example 1, fully demonstrating the synergistic effect of the process features of this invention as an organic whole.

[0196] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Various changes made within the scope of knowledge possessed by those skilled in the art without departing from the concept of the present invention still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a bran-based, aromatic wine starter, characterized in that, Includes the following steps: S1. Raw material pretreatment: The carrier, cellulase, pectinase, saccharifying enzyme, neutral protease and lipase are sieved to remove impurities. S2. Stepwise premixing: Under an ambient temperature below 25°C, the sieved components are divided into two groups for premixing. The first group includes the carrier, saccharifying enzyme, and cellulase, and is premixed at ≤25°C for 10–20 minutes. The second group includes pectinase, neutral protease, and lipase, and is premixed at ≤20°C for 10–20 minutes. Then, the two premixes are mixed together at ≤20°C for 20–40 minutes. S3, stepped ultrafine grinding: The mixture obtained from S2 is first coarsely ground to 150-250 mesh, and then air-flow ultrafine grinding is carried out to 800-1000 mesh. The entire grinding process is carried out at 15-25℃ for 0.5-1.5 hours. S4. Low-temperature vacuum drying: The ultrafine powder obtained in S3 is vacuum dried at a temperature below 30°C to reduce the water activity to below 0.

2. S5. Low-temperature mixing: The dried ultrafine powder obtained in S4 is mixed evenly with ester-producing active dry yeast and Aspergillus niger bran powder at a temperature below 25°C. S6. Packaging: Vacuum package the mixture obtained in S5 to obtain the finished product.

2. The preparation method according to claim 1, characterized in that, In S1, the cellulase and pectinase are sieved through a mesh size of 40-100, the saccharifying enzyme, neutral protease and lipase are sieved through a mesh size of 20-80, and the carrier is sieved through a mesh size of 20-80.

3. The preparation method according to claim 1, characterized in that, In step S2, the premixing temperature of the second group is 3-8°C lower than that of the first group; the temperature of the total mixture is not higher than that of the premixing temperature of the second group; and the rotation speed of the stirring tank is 40-60 rpm.

4. The preparation method according to claim 1, characterized in that, In step S3, the material is first coarsely pulverized to 150-250 mesh, and then air-jet pulverized to 800-1000 mesh. The entire pulverization process is carried out at 15-25°C for 0.5-1.5 hours. During air-jet pulverization, the relative humidity in the pulverization chamber is controlled to be ≤30%.

5. The preparation method according to claim 1, characterized in that, The neutral protease has an enzyme activity of 50,000 to 100,000 U / g, and the lipase has an enzyme activity of 10,000 to 50,000 U / g.

6. The preparation method according to claim 1, characterized in that, In step S4, the vacuum drying time is 2 to 6 hours, and the vacuum degree is -0.08 to -0.1 MPa.

7. A type of bran-based, light-aroma wine starter, characterized in that, By mass percentage, it includes the following components: carrier 0%–12%, ester-producing active dry yeast 5%–15%, Aspergillus niger bran powder 15%–25%, cellulase 10%–25%, pectinase 10%–20%, saccharifying enzyme 5%–15%, neutral protease 3%–10%, and lipase 2%–8%, with the sum of the mass percentages of each component being 100%.

8. The bran-based light-aroma liquor starter according to claim 7, characterized in that, The yeast is prepared by any one of claims 1 to 6, and the saccharification power of the yeast is ≥1000U / g.

9. The bran-based light-aroma liquor starter according to claim 8, characterized in that, When the yeast is used in brewing, under the conditions that the amount of yeast added is 0.5% to 2% of the raw material mass, the fermentation temperature is 25 to 30°C, and the fermentation cycle is 3 to 5 days, the starch conversion rate is ≥95%.

10. The application of the bran-fermented light-aroma koji as described in any one of claims 7 to 9 in the brewing of bran-fermented light-aroma baijiu.

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