Sauce-flavor daqu and preparation method therefor

Abstract

The present invention belongs to the technical field of sauce-flavor Daqu manufacturing. Disclosed are a sauce-flavor Daqu and a preparation method therefor. The raw material for preparing the sauce-flavor Daqu comprises 50-100 wt% of fermented highland barley powder and 0-50 wt% of wheat flour, and further comprises grain-moistening water at 38-42% of the total mass of the fermented highland barley powder and wheat flour, and a starter culture powder at 3-8% of the mass of the wheat flour. The sauce-flavor Daqu is prepared by means of the process flows comprising fermented highland barley powder preparation, wheat flour preparation, wheat flour and fermented highland barley powder mixing, Daqu brick molding, placement and fermentation, Daqu discharging and warehousing, and storage. The sauce-flavor Daqu solves the problems of slow and unsatisfactory fermentation caused by the high viscosity of Daqu bricks prepared by using highland barley as the raw material, and the problem of the low abundance of Scopulibacillus daqui in Sichuanese sauce-flavor Daqu, and further optimizes the richness of sauce-flavor in Sichuanese sauce-flavor Daqu and improves the overall quality of the sauce-flavor Daqu.

Description

A soy sauce-flavored daqu (fermented rice starter) and its preparation method Technical Field

[0001] This invention belongs to the fields of manufacturing technology of soy sauce-flavored koji and processing of specialty agricultural products and agricultural industrialization. It relates to a production method for improving the overall quality of Sichuan-style soy sauce-flavored koji, specifically to a soy sauce-flavored koji and its preparation method. Background Technology

[0002] Barley, a type of naked barley, is mainly grown in Tibet, Qinghai, Sichuan (Ganzi and Aba prefectures), and Gansu. The utilization of barley is still at a regional, low-processing stage, primarily involving simple processing into tsampa or brewing barley wine. It is one of the most distinctive crops of the Qinghai-Tibet Plateau. Barley is rich in β-glucan, dietary fiber, oleic acid, and other beneficial components, and has the characteristic of helping to lower blood pressure, blood sugar, and cholesterol. However, the high hardness and thick cell walls of barley grains, along with the lack of the structural and functional characteristics of wheat gluten protein, limit its application in food processing. In the field of soy sauce-flavored koji (fermented barley starter) manufacturing technology, many studies and production have found that using barley as a raw material for koji preparation results in slow fermentation and unsatisfactory fermentation due to the high viscosity of the starter. Therefore, optimizing the applicability of barley koji-making processes is essential.

[0003] As a microbial inoculant, saccharification and fermentation agent, and aroma-generating agent in the brewing process of soy sauce-flavored baijiu, Daqu (a type of starter culture) is a crucial factor influencing the quality of baijiu. Daqu is made from wheat, barley, production water, and mother koji as the main raw materials, with new and old rice straw as auxiliary materials, using a raw material koji-making process and high-temperature fermentation. The entire preparation environment is open, so microorganisms from wheat, koji-making water, rice straw, operating tools, and the environment, except for the mother koji, can directly enter the koji-making microbial community, making them an important source of Daqu microorganisms. Due to its complex production process, reliance on experience for process control, and significant regional influences, the quality of Daqu is unstable and varies greatly across regions. In particular, the low content of pyrazines and the low abundance of *Scopulibacillus* in Sichuan-style Daqu affect the overall quality of soy sauce-flavored baijiu.

[0004] Therefore, in response to the above-mentioned technical problems, it is urgent to study a production process that uses highland barley as raw material to make koji while improving the overall quality of soy sauce-flavored koji. Summary of the Invention

[0005] The technical problems to be solved by the present invention are the following: the fermentation effect of barley koji making is affected by the sticking of koji blanks, and the overall quality of sauce-flavored koji is unstable due to the low content of pyrazine substances and the low abundance of Bacillus rock spp. in koji.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] In a first aspect, the present invention provides a soy sauce-flavored koji, the raw materials for making koji include 50-100% barley fermentation powder and 0-50% wheat flour by mass percentage, and also include 38-42% of the total mass of barley fermentation powder and wheat flour as grain-moistening water and 3-8% of the mass of wheat flour as mother koji powder.

[0008] In the above-mentioned soy sauce-flavored koji, the preparation method of the barley fermentation powder is as follows: the barley grain is moistened with water and then piled up for moistening; the moistened barley is crushed to obtain barley powder; the crushed mother koji is added and mixed evenly, and then piled up for fermentation.

[0009] Furthermore, the amount of water used for moistening the barley is 8-20% of the weight of the raw barley, and the moistening time is 6-12 hours.

[0010] Furthermore, 30-50% of the barley flour is fine powder that can pass through a 1.2mm sieve, while no more than 5% is whole barley grains.

[0011] Furthermore, the amount of mother koji powder added is 3-8% of the mass of highland barley flour, and the fermentation time is 6-24 hours.

[0012] In the above-mentioned method for preparing soy sauce-flavored koji or barley fermentation powder, the method for preparing the mother koji powder is as follows: pulverize mature soy sauce-flavored koji that has been stored for 3 to 8 months, and the fine powder that can pass through a 1.2 mm sieve accounts for 60 to 80%.

[0013] In the above-mentioned soy sauce-flavored koji, the method for preparing wheat flour is as follows: wheat grains are moistened with water, and then piled up for moistening; the moistened wheat is then crushed to obtain wheat flour.

[0014] Furthermore, the amount of water used to moisten the grain is 1-10% of the weight of the raw wheat grain, and the grain is piled up for moistening for 1-12 hours.

[0015] Furthermore, 35-55% of the wheat flour is fine powder that can pass through a 1.2mm sieve, while no more than 3% is whole wheat grain.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned soy sauce-flavored daqu (a type of starter culture), specifically including the following steps:

[0017] (1) Barley yeast and wheat flour are mixed to obtain a mixed powder, and then mother koji powder and grain moistening water are added to mix the powder to obtain koji.

[0018] (2) The koji material is shaped by manual treading or mechanical pressing according to the specifications of the koji mold to make koji blanks;

[0019] (3) The koji blanks are transferred to the fermentation room for koji preparation and fermentation. The process control during fermentation is as follows: when the temperature rises to 60-65℃, the first opening of doors and windows and turning of koji are carried out, and the humidity of the koji room is above 80%; after the first turning of koji, when the temperature rises to 58-60℃, the second opening of doors and windows and turning of koji are carried out, and the humidity of the koji room is above 70%; when the temperature rises to 52-55℃ after the second turning of koji, doors and windows are opened for ventilation and dehumidification.

[0020] (4) After the fermentation of the koji is completed, the koji is removed and stored in the warehouse to obtain the sauce-flavored koji.

[0021] In the above-mentioned method for preparing soy sauce-flavored koji, in step (1), barley fermentation powder accounts for 50-100% of the mass of the mixed powder, wheat flour accounts for 0-50% of the mass of the mixed powder, the amount of mother koji powder added is 3-8% of the mass of wheat flour, and the amount of grain moistening water added is 38-42% of the mass of the mixed powder.

[0022] In the preparation method of the above-mentioned soy sauce-flavored koji, in step (3), when placing the koji, first lay a layer of rice straw 15-30cm thick in the fermentation room, and then stack the koji blanks in the fermentation room in an orderly manner with "three horizontal and three vertical" sides; and after each layer of koji is laid, new and old rice straw and a certain amount of water are added for inoculation, heat preservation and moisture retention.

[0023] In the above-mentioned method for preparing soy sauce-flavored koji, in step (4), the fermentation time is 38 to 42 days, and the koji blanks can be removed and stored when the moisture content drops to 15%.

[0024] In the above-mentioned method for preparing soy sauce-flavored koji, in step (4), the storage period of the koji blank is 3 to 6 months, and the moisture content of the finished koji is controlled to be below 13%.

[0025] Beneficial effects: This invention proposes a fermentation process for barley yeast powder, which produces a high-quality yeast powder containing a large amount of 2,3-butanedione and 3-hydroxy-2-butanone, precursors for the formation of tetramethylpyrazine. This invention innovatively uses these precursors in the preparation of soy sauce-flavored koji, increasing the abundance of *Scopulibacillus* in the koji and simultaneously increasing the content of pyrazine substances, thereby improving the overall quality of the koji and overcoming the instability in koji quality caused by traditional koji preparation methods and regional factors. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the production process of the present invention. Detailed Implementation

[0027] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0028] This invention discloses a method for preparing a soy sauce-flavored daqu (a type of starter culture), the process flow of which is shown in Figure 1, and specifically includes the following steps.

[0029] 1. Preparation of highland barley baking powder

[0030] 1-1 Select plump, mold-free, sprout-free, insect-free, and impurity-free highland barley as the raw material for koji making. Moisten the highland barley raw material with 8-20% production water. In summer, pile the highland barley in room temperature water for 6-12 hours to moisten it. In winter, the water temperature for moistening the highland barley should be 90-100℃, and the highland barley should be piled up for 6-8 hours to moisten it. If it is found to be too dry, add 1-3% water based on the amount of highland barley raw material.

[0031] 1-2 Crush the soaked barley into powder, ensuring that "the core is rotten but the husk is not." Fine powder that can pass through a 1.2mm sieve should account for 30-50%, and whole barley grains should not exceed 5%. The powder should be slightly coarser in winter and slightly finer in summer to obtain barley flour.

[0032] 1-3 Add 3-8% of the weight of barley koji powder to barley powder and mix. Use a production line winch, mixer or manual mixing to mix evenly. After the mixture is piled up and fermented for 6-24 hours, barley fermented powder is obtained.

[0033] Preferably, the preparation method of the mother koji powder is as follows: the mature soy sauce-flavored koji that has been stored for 3 to 8 months is pulverized, and the fine powder that can pass through a 1.2 mm sieve accounts for 60 to 80%; the powder is slightly finer and the amount added is slightly more in winter, and slightly coarser and the amount added is slightly less in summer.

[0034] 2. Preparation of wheat flour

[0035] 2-1 Select plump wheat grains that are free from mold, sprouting, insect infestation, and impurities as the raw material for compound koji making. Moisten the wheat grains with 1-10% production water, and then pile them up to moisten for 1-12 hours. If they are found to be too dry, add 1-3% water based on the amount of wheat raw material.

[0036] 2-2 The moistened wheat is crushed, requiring "the heart to be rotten but the husk to be intact". The fine powder that can pass through a 1.2mm sieve should account for 35-55%, and the whole wheat grains should not exceed 3% to obtain wheat flour.

[0037] 3. Preparation of Soy Sauce Aroma Daqu

[0038] 3-1 Mix barley yeast and wheat flour in a mass ratio of 5-10:0-5, add 3-8% of the mother koji powder by weight of wheat flour, add water and mix. Use a production line winch, mixer or manual mixing to mix evenly. The koji material should be loose and free of raw dough. It should be able to be formed into a ball by hand without sticking to the hands. After kneading, the palms should be moist but not waterlogged, and the consistency should be uniform.

[0039] 3-2 The koji material is manually treaded into shape according to the specifications of the large koji mold, or mechanically pressed into shape. The koji blank should have neat four corners, a smooth surface, be treaded tightly around the edges, be slightly loose in the middle, have uniform thickness, and be free of missing edges or corners. The koji blank should be moist and elastic and should not crack when placed upright.

[0040] 3-3 The prepared koji blanks are transported to the koji room for fermentation. The fermentation room requires a layer of straw about 15-30cm thick to be laid first. Then, the koji blanks are stacked in an orderly manner with three horizontal and three vertical rows. After each layer of koji is laid, new and old straw and a certain amount of water are added for inoculation, heat preservation and moisture retention. According to the process requirements, when the temperature of the koji blanks rises to a certain temperature, process control and turning operations are carried out. When the temperature rises to 60-65℃, the first opening of doors and windows and turning operation are carried out, and the humidity of the koji room is above 80%. After the first turning operation, when the temperature rises to 58-60℃, the second opening of doors and windows and turning operation are carried out, and the humidity of the koji room is above 70%. When the temperature rises to 52-55℃ after the second turning operation, doors and windows are opened for ventilation and moisture removal.

[0041] 3-4 Ferment for 38-42 days. When the moisture content of the koji blocks drops to 15%, the fermented koji blocks can be disassembled and stored. Before storage, the straw on the koji blocks should be manually removed and transferred to a clean, dry and ventilated storage room for orderly stacking and storage. During storage, the storage room should be closed and the moisture should be removed intermittently as appropriate. The storage period for the koji blocks is required to be 3-6 months. When the moisture content of the finished koji blocks is controlled to be below 13%, they can be put into production and use.

[0042] Preferably, when the temperature is low in winter, a layer of straw mat should be covered on the koji pile to prevent mold growth on the koji due to low temperature and high humidity.

[0043] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0044] Example

[0045] I. Preparation of Soy Sauce Aroma Daqu

[0046] In order to better highlight the innovative points of the present invention, a process using 100% wheat is used as a comparative example to demonstrate the technical advantages of the present invention through comparison of the same batch of tests.

[0047] A method for preparing a soy sauce-flavored high-temperature koji (taking the production of koji in a fermentation room as an example) includes the following steps:

[0048] Sixteen tons of high-quality wheat were selected, requiring plump grains, free from mold, sprouting, insect infestation, and impurities. The wheat was soaked in water at 95℃ with 3% added, and the soaking time was 1 hour. After soaking, the wheat was ground using a steel mill. The sensory requirements were that there were no whole wheat grains, no coarse lumps, and the texture was neither greasy nor rough to the touch, with no rotten core or husk. The fine powder that passed through a 1.2mm sieve accounted for 40%, thus obtaining wheat flour.

[0049] Wheat flour and 6% (by weight of wheat) of mother koji powder (70% of which is fine powder passing through a 1.2mm sieve) are mixed evenly, and room temperature water is added to control the moisture content of the koji dough at 40%. The mixture is then made into bundles of koji. Fresh koji dough is manually placed on pallet carts and transported to the koji room for fermentation. A total of 2400 bundles are placed per room. After fermentation, the doors and windows are closed for fermentation. The first turning of the koji occurs on day 8; the second turning occurs on day 16; and the doors and windows are opened on day 21 for ventilation and moisture removal. The koji is removed and stored after 40 days of fermentation. Samples are taken for sensory evaluation, biochemical analysis, flavor component analysis, and microbial community analysis.

[0050] Experimental Example 1 describes the production of the same type of soy sauce-flavored high-temperature koji as the control example (taking the production of koji from one fermentation room as an example), including the following steps:

[0051] First, select 8 tons of high-quality highland barley, ensuring the grains are plump, free from mold, sprouting, insect infestation, and impurities. Use 95℃ water for moistening, adding 15% of the starter culture, and moisten for 6 hours. After moistening, grind the barley using a steel mill, ensuring the core is intact but the husk is intact, with 30% of the powder passing through a 1.2mm sieve. Mix the barley powder and 6% of the starter culture (70% of which should pass through a 1.2mm sieve) evenly, and then pile them for fermentation for 12 hours to obtain barley fermentation powder.

[0052] Eight tons of high-quality wheat were selected, and the wheat was soaked in water at 95℃ with 3% added for 1 hour. After soaking, the wheat was ground using a steel mill. The sensory requirements were that there were no whole wheat grains, no coarse lumps, and the wheat was not greasy or rough to the touch, with no rotten core or rotten husk. The fine powder that passed through a 1.2mm sieve accounted for 40%, thus obtaining wheat flour.

[0053] Barley yeast, wheat flour, and 6% (by weight of wheat) of the starter culture powder are mixed evenly, and room temperature water is added to control the moisture content of the starter culture at 40%. The mixture is then made into bundles of starter culture. Fresh starter culture is manually placed on pallet carts and transported to the starter culture room for placement. A total of 2400 bundles are placed per room. After placement, the doors and windows are closed for fermentation. The first turning of the starter culture occurs on day 8; the second turning occurs on day 16; and on day 21, the doors and windows are opened for ventilation and moisture removal. After 40 days of fermentation, the starter culture is removed and stored. Samples are taken for sensory evaluation, biochemical analysis, flavor component analysis, and microbial community analysis.

[0054] Experimental Example 2 produces the same type of soy sauce aroma type high-temperature koji as the control example (taking the production of koji from one fermentation room as an example), including the following steps:

[0055] First, select 11.2 tons of high-quality highland barley, ensuring the grains are plump, free from mold, sprouting, insect infestation, and impurities. Use 95℃ water for moistening, adding 15% of the starter culture, and moisten for 6 hours. After moistening, grind the barley using a steel mill, ensuring the core is intact but the husk is intact, with 30% of the powder passing through a 1.2mm sieve. Mix the barley powder and 6% of the starter culture (70% of which should pass through a 1.2mm sieve) evenly, and then pile them for fermentation for 12 hours to obtain barley fermentation powder.

[0056] Then select 4.8 tons of high-quality wheat, soak it in water at 95℃, add 3% of the additive, and soak it for 1 hour. After soaking, grind it with a steel mill. The sensory requirements are that there are no whole wheat grains, no coarse lumps, and it is not greasy or rough to the touch. The fine powder that passes through a 1.2mm sieve accounts for 40% of the total fine powder, which is then obtained as wheat flour.

[0057] Barley yeast, wheat flour, and 6% mother koji powder are mixed evenly, and room temperature water is added to control the moisture content of the koji blanks at 40%. Then, the koji is made into bundles. Fresh koji blanks are manually placed on pallet carts and transported to the koji room for placement. A total of 2400 bundles are placed per room. After placement, the doors and windows are closed for fermentation. The first turning of the koji occurs on day 8; the second turning occurs on day 16; and on day 21, the doors and windows are opened for ventilation and moisture removal. After 40 days of fermentation, the koji is removed and stored. Samples are taken for sensory, biochemical, flavor component, and microbial community testing.

[0058] Experimental Example 3 describes the production of the same type of soy sauce-flavored high-temperature koji as the control example (taking the production of koji from one fermentation room as an example), including the following steps:

[0059] First, select 16 tons of high-quality highland barley, ensuring the grains are plump, free from mold, sprouting, insect infestation, and impurities. Use 95℃ water for wetting, adding 15% of the starter culture, and wetting for 6 hours. After wetting, grind the barley using a steel mill, ensuring the core is intact but the husk is intact, with 30% of the powder passing through a 1.2mm sieve. Mix the barley powder with 6% of the starter culture (70% of which should pass through a 1.2mm sieve) evenly and ferment for 12 hours to obtain barley yeast.

[0060] The barley yeast is mixed with room temperature water, and the moisture content of the koji (fermentation starter) is controlled at 40%. Then, the koji is made into individual bundles. Fresh koji are manually placed on pallet carts and transported to the koji room for fermentation. A total of 2400 bundles are placed per room. After fermentation, the doors and windows are closed for fermentation. The first turning of the koji occurs on day 8; the second turning occurs on day 16; and on day 21, the doors and windows are opened for ventilation and moisture removal. After 40 days of fermentation, the koji is removed and stored. Samples are taken for sensory, biochemical, flavor component, and microbial community testing.

[0061] II. Detection of Soy Sauce Aroma Daqu

[0062] The sensory properties, physicochemical indicators, pyrazine content, and microbial community of the koji prepared in Experiments 1-3 and the comparative examples are shown in Tables 1-4.

[0063] Table 1 Sensory results of soy sauce-flavored daqu obtained by different preparation methods.

[0064] As shown in Table 1, the soy sauce-flavored koji made with wheat and barley fermentation powder has a prominent soy sauce aroma, roasted aroma, and fermented black bean aroma, and the koji aroma is pleasant and comfortable. The overall sensory effect is better than the control example.

[0065] Table 2. Physicochemical results of soy sauce-flavored daqu obtained by different preparation methods.

[0066] As shown in Table 2, the physicochemical properties of the koji made from wheat and barley fermentation powder are normal.

[0067] Table 3. Results of pyrazine content in soy sauce-flavored daqu obtained by different preparation methods.

[0068] As shown in Table 3, the use of wheat and barley fermentation powder to make soy sauce-flavored koji significantly increased the content of tetramethylpyrazine, the main pyrazine compound in the koji, thus optimizing the rich soy sauce flavor of Sichuan-style koji and improving the overall quality of the koji.

[0069] Table 4. Abundance (%) of microbial communities in soy sauce-flavored daqu obtained by different preparation methods

[0070] As shown in Table 4, the abundance of *Scopulibacillus* in the koji made from wheat and barley fermentation powder was significantly increased.

[0071] As shown in Tables 1-4, the production process of this invention can solve the problem of low abundance of *Scopulibacillus* in Sichuan-style Daqu, overcome the microecological problems of Daqu caused by traditional Sichuan-style Daqu preparation process and regional factors, and improve the quality of Daqu from the source.

Claims

1. A type of soy sauce-flavored koji (fermented grain starter), characterized in that: The raw materials for making koji, by weight percentage, include 50-100% barley yeast and 0-50% wheat flour, as well as 38-42% of the total weight of barley yeast and wheat flour in soaking water and 3-8% of the weight of wheat flour in mother koji powder.

2. The soy sauce-flavored koji according to claim 1, characterized in that: The preparation method of barley fermentation powder is as follows: add water to the raw barley grain to moisten it, and then pile it up to moisten it; crush the moistened barley to obtain barley powder; add mother koji powder and mix evenly, and pile it up to ferment.

3. The soy sauce-flavored koji according to claim 2, characterized in that: The preparation method of highland barley baking powder shall meet at least one of the following requirements: The amount of water used to moisten the barley is 8-20% of the weight of the raw barley, and the moistening time is 6-12 hours. Fine barley flour that can pass through a 1.2mm sieve accounts for 30-50%, while whole barley grains account for no more than 5%. The amount of mother koji powder added is 3-8% of the mass of highland barley flour, and the fermentation time is 6-24 hours.

4. The soy sauce-flavored koji according to any one of claims 1 to 3, characterized in that: The preparation method of the mother koji powder is as follows: the mature soy sauce-flavored koji that has been stored for 3 to 8 months is pulverized, and the fine powder that can pass through a 1.2 mm sieve accounts for 60 to 80%.

5. The soy sauce-flavored koji according to claim 1, characterized in that: The preparation method of wheat flour is as follows: wheat grains are moistened with water, and then piled up to moisten; the moistened wheat is then crushed to obtain wheat flour; The amount of water used to moisten the grain is 1-10% of the weight of the raw wheat grain, and the grain is piled up and moistened for 1-12 hours. Fine wheat flour that can pass through a 1.2mm sieve accounts for 35-55%, while whole wheat grains account for no more than 3%.

6. The method for preparing the soy sauce-flavored daqu according to any one of claims 1 to 5, characterized in that, Specifically, the steps include the following: (1) Barley yeast and wheat flour are mixed to obtain a mixed powder, and then mother koji powder and grain moistening water are added to mix the powder to obtain koji. (2) The koji material is shaped by manual treading or mechanical pressing according to the specifications of the koji mold to make koji blanks; (3) The koji blanks are transferred to the fermentation room for koji preparation and fermentation. The process control during fermentation is as follows: when the temperature rises to 60-65℃, the first opening of doors and windows and turning of koji are carried out, and the humidity of the koji room is above 80%; after the first turning of koji, when the temperature rises to 58-60℃, the second opening of doors and windows and turning of koji are carried out, and the humidity of the koji room is above 70%; when the temperature rises to 52-55℃ after the second turning of koji, doors and windows are opened for ventilation and dehumidification. (4) After the fermentation of the koji is completed, the koji is removed and stored in the warehouse to obtain the sauce-flavored koji.

7. The method for preparing soy sauce-flavored daqu according to claim 6, characterized in that: In step (1), barley yeast accounts for 50-100% of the mass of the mixed powder, wheat flour accounts for 0-50% of the mass of the mixed powder, the amount of mother yeast powder added is 3-8% of the mass of wheat flour, and the amount of grain soaking water added is 38-42% of the mass of the mixed powder.

8. The method for preparing soy sauce-flavored daqu according to claim 6, characterized in that: In step (3), when placing the koji, first lay a layer of straw 15-30cm thick in the fermentation room, and then stack the koji blanks in an orderly manner with three horizontal and three vertical rows in the fermentation room; and after each layer of koji blanks is laid, new and old straw and a certain amount of water are added for inoculation, heat preservation and moisture retention.

9. The method for preparing soy sauce-flavored daqu according to claim 6, characterized in that: In step (4), the fermentation time is 38 to 42 days. Once the moisture content of the koji cake drops to 15%, it can be removed from the mold and stored.

10. The method for preparing soy sauce-flavored daqu according to claim 6, characterized in that: In step (4), the storage period of the koji blank is 3 to 6 months, and the moisture content of the finished koji is controlled to be below 13%.

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