A brewing method for realizing flavor enhancement and odor control of yellow rice wine based on compound wheat koji

Abstract

The present application relates to the technical field of yellow rice wine brewing and flavor control, and discloses a brewing method for realizing yellow rice wine flavor enhancement and odor control based on compound wheat starter.The method realizes the brewing method of "flavor enhancement and odor control" by using single or compound of block starter, inoculated raw wheat starter and explosive wheat starter under the condition of constant total starter amount.The results show that under the condition of the same total starter amount, the compound of inoculated raw wheat starter and explosive wheat starter at a ratio of 1:1 can significantly increase key aroma substances such as ethyl acetate, ethyl octanoate, ethyl decanoate and phenethyl alcohol;the compound of block starter, inoculated raw wheat starter and explosive wheat starter at a ratio of 1:1:1 can inhibit characteristic substances such as 2-methyltetrahydrothiophene and 4-vinylguaiacol.The method has clear process window and good repeatability, and is suitable for flavor optimization and targeted development of yellow rice wine products.

Description

Technical Field

[0001] This invention relates to a brewing method for enhancing the aroma and controlling off-flavors of rice wine based on compound wheat koji, belonging to the field of rice wine brewing and flavor control technology. Background Technology

[0002] As a traditional fermented beverage in my country, Shaoxing wine's flavor development relies on a complex process of enzymatic saccharification and microbial fermentation. Wheat koji (a type of starter culture) plays a crucial role in Shaoxing wine brewing, providing both saccharifying enzymes and constructing the fermentation microecology. It determines the starch degradation rate, fermentation process, and the generation and transformation of volatile flavor compounds such as esters, alcohols, phenols, and sulfur-containing compounds. Different types of wheat koji (such as block koji, inoculated raw wheat koji, and popped wheat koji) differ in their microbial composition and enzyme activity; using a single type of koji can easily lead to a monotonous aroma structure or flavor deviation. Blended wheat koji can be used for flavor optimization, but whether blended koji exhibits quantifiable synergistic or antagonistic effects, and how to enhance fruity / floral aromas while suppressing characteristic off-flavors such as sulfur and phenolic tastes, remains unknown. Summary of the Invention

[0003] To address the shortcomings of the existing technology, the present invention aims to provide a brewing method for rice wine that achieves both aroma enhancement and off-flavor control by using different types of wheat koji alone or in combination, under the condition of a constant total amount of koji. Furthermore, by quantifying the non-additive effect generated by the compounding through synergy and relative synergy, the present invention solves the technical problem in the existing technology of lacking the ability to enhance the fruit / floral aroma of rice wine while suppressing characteristic off-flavor substances such as sulfur and phenolic tastes.

[0004] The first technical solution provided by this invention is a method for brewing rice wine, the method comprising the following steps: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is a combination of two or three of the following: block yeast, inoculated raw wheat yeast and popped wheat yeast. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

[0005] In some embodiments, in step (1), the rice saccharification liquid culture medium is prepared by mixing raw glutinous rice and water at a mass ratio of 1:4, adding 2‰ liquefying enzyme and 1‰ saccharifying enzyme based on the mass of raw rice, and adding 10% to 15% of koji (a type of starter culture) based on the mass of raw rice. The mixture is then saccharified and liquefied at 55℃ to 65℃ for 4 to 6 hours until the sugar content is ≥13 °Brix. After filtration, the mixture is sterilized at 115℃ for 20 minutes.

[0006] In some embodiments, the seed culture is prepared using brewing yeast jiangnan1# (CCTCC NO:M 2021523); brewing yeast jiangnan1# is inoculated into rice saccharification liquid culture medium at an inoculation rate of 3%, and cultured at 28℃ and 150 r / min for 36 h to obtain the yeast starter.

[0007] In some implementations, in step (2), the total amount of yeast added is 10% to 20% of the mass of glutinous rice.

[0008] In some embodiments, the glutinous rice is 100% to 200% of the weight of glutinous rice, the water content is 80% to 160% of the weight of glutinous rice, and the yeast content is 5% to 20% of the weight of glutinous rice.

[0009] In some embodiments, the method for preparing glutinous rice is as follows: weigh glutinous rice and soak it in water until it is fully hydrated; after soaking, drain the rice to obtain wet rice, steam the wet rice for 20-30 minutes until the rice is cooked but not mushy and there is no white core in the rice grains; let it cool until the rice temperature is below 60°C for later use.

[0010] In some implementations, the soaking time is 1 to 3 days.

[0011] In some implementations, in step (2), the aroma-enhancing compound is a 1:1 mixture of raw wheat koji and popped wheat koji.

[0012] In some implementations, in step (2), the odor-controlling and aroma-coordinating compound is a mixture of block koji, inoculated raw wheat koji, and popped wheat koji in a 1:1:1 ratio.

[0013] The second technical solution provided by the present invention is a method for increasing the aroma of rice wine. The method involves adding wheat koji during the rice wine brewing process, which is prepared by mixing raw wheat koji and popped wheat koji in a 1:1 ratio.

[0014] In some embodiments, the flavoring substances that produce the aroma include ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol.

[0015] In some implementations, the following steps are included: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is prepared by mixing raw wheat yeast and popped wheat yeast in a 1:1 ratio. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

[0016] In some embodiments, the rice saccharification culture medium is prepared by mixing raw glutinous rice and water at a mass ratio of 1:4, adding 2‰ liquefying enzyme and 1‰ saccharifying enzyme based on the mass of raw rice, and adding 10% to 15% raw wheat koji based on the mass of raw rice. The mixture is then saccharified and liquefied at 55℃ to 65℃ for 4 to 6 hours until the sugar content is ≥13 °Brix. After filtration, the mixture is sterilized at 115℃ for 20 minutes.

[0017] In some embodiments, the seed culture is prepared using brewing yeast jiangnan1# (CCTCC NO:M 2021523); brewing yeast jiangnan1# is inoculated into rice saccharification liquid culture medium at an inoculation rate of 3%, and cultured at 28℃ and 150 r / min for 36 h to obtain the yeast starter.

[0018] In some implementations, in step (2), the total amount of yeast added is 10% to 20% of the mass of glutinous rice.

[0019] In some embodiments, the glutinous rice is 100% to 200% of the weight of glutinous rice, the water content is 80% to 160% of the weight of glutinous rice, and the yeast content is 5% to 20% of the weight of glutinous rice.

[0020] In some embodiments, the method for preparing glutinous rice is as follows: weigh glutinous rice and soak it in water until it is fully hydrated; after soaking, drain the rice to obtain wet rice, steam the wet rice for 20-30 minutes until the rice is cooked but not mushy and there is no white core in the rice grains; let it cool until the rice temperature is below 60°C for later use.

[0021] In some implementations, the soaking time is 1 to 3 days.

[0022] In some implementations, the soaking time is 3 to 5 days.

[0023] The third technical solution provided by the present invention is a method for reducing off-flavors in rice wine while maintaining aroma harmony. The method involves adding wheat koji during the rice wine brewing process, which is prepared by compounding block koji, inoculated raw wheat koji, and popped wheat koji in a ratio of 1:1:1.

[0024] In some embodiments, the compounds that produce the odor include 2-methyltetrahydrothiophene and 4-vinylguaiacol.

[0025] In some implementations, the following steps are included: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is prepared by mixing block yeast, inoculated raw wheat yeast and popped wheat yeast in a ratio of 1:1:1. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

[0026] In some embodiments, the rice saccharification culture medium is prepared by mixing raw glutinous rice and water at a mass ratio of 1:4, adding 2‰ liquefying enzyme and 1‰ saccharifying enzyme based on the mass of raw rice, and adding 10% to 15% raw wheat koji based on the mass of raw rice. The mixture is then saccharified and liquefied at 55℃ to 65℃ for 4 to 6 hours until the sugar content is ≥13 °Brix. After filtration, the mixture is sterilized at 115℃ for 20 minutes.

[0027] In some embodiments, the seed culture is prepared using brewing yeast jiangnan1# (CCTCC NO:M 2021523); brewing yeast jiangnan1# is inoculated into rice saccharification liquid culture medium at an inoculation rate of 3%, and cultured at 28℃ and 150 r / min for 36 h to obtain the yeast starter.

[0028] In some implementations, in step (2), the total amount of yeast added is 10% to 20% of the mass of glutinous rice.

[0029] In some embodiments, the glutinous rice is 100% to 200% of the weight of glutinous rice, the water content is 80% to 160% of the weight of glutinous rice, and the yeast content is 5% to 20% of the weight of glutinous rice.

[0030] In some embodiments, the method for preparing glutinous rice is as follows: weigh glutinous rice and soak it in water until it is fully hydrated; after soaking, drain the rice to obtain wet rice, steam the wet rice for 20-30 minutes until the rice is cooked but not mushy and there is no white core in the rice grains; let it cool until the rice temperature is below 60°C for later use.

[0031] In some implementations, the soaking time is 1 to 3 days.

[0032] In some implementations, the soaking time is 3–5 days.

[0033] The fourth technical solution provided by this invention is the application of the method described in the first technical solution in improving the flavor and quality of rice wine.

[0034] In some embodiments, the improvement of rice wine quality includes: (1) increasing aroma substances including ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol; and (2) inhibiting the characteristic substances of 2-methyltetrahydrothiophene and 4-vinylguaiacol, thereby controlling off-flavors and improving aroma harmony.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Under the same total amount of koji, specific compound koji can significantly increase the relative linear expected value of key aroma substances such as ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol, demonstrating a synergistic aroma-enhancing effect. (2) The three-component compound can significantly inhibit characteristic substances such as 2-methyltetrahydrothiophene and 4-vinylguaiacol, which is beneficial to control off-odors and improve aroma coordination. (3) The physicochemical indicators such as alcohol content, reducing sugar, total acid and amino acid nitrogen of each scheme are in a similar range, indicating that the flavor difference is mainly due to the difference in the use of koji and the influence of its combination on metabolic distribution, and the process has good repeatability. Detailed Implementation

[0036] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0037] Technical terms: The "wheat koji" mentioned in this invention refers to a saccharification and fermentation agent made from wheat as raw material through natural or pure culture, and is the core koji used in the brewing of Chinese rice wine. It is mainly based on wheat and produces a rich enzyme system and flavor substances through the metabolism of microorganisms (Aspergillus, Rhizopus, yeast, etc.), which not only breaks down starch into sugar, but also endows the wine with complex aroma and taste.

[0038] The "block koji" mentioned in this invention refers to a type of koji classified according to its shape and form. It refers to koji made by crushing raw materials (such as wheat, barley, peas, etc.), adding water, pressing them into brick or cake shapes, and then cultivating them.

[0039] The "inoculated raw wheat koji" described in this invention refers to an improvement on traditional raw wheat koji. During koji production, selected superior microbial strains (such as pure cultures of Aspergillus oryzae and Rhizopus) are artificially introduced into the raw materials. However, the overall koji-making process still maintains the method of "raw material, pressing, and natural or semi-natural cultivation." Specifically, the "inoculated raw wheat koji" of this invention is a pure culture of Aspergillus flavus SU-16 purchased from Shanghai Jin Feng Winery Co., Ltd. A. flavus Raw wheat koji containing Aspergillus flavus SU-16 (SU-16) A. flavus SU16) is recorded in the document "Integrated multi-omics analysis unveils metabolites-mediatedmicrobial interactions: dynamic regulation and metabolic division of A.flavus SU-16 and S. cerevisiae HJ during co-fermentation".

[0040] The "popped wheat koji" mentioned in this invention refers to a method of processing wheat raw materials by first treating them at high temperatures to make them pop (similar to popcorn, but without oil), and then making koji or using them directly for brewing.

[0041] The "starter culture" mentioned in this invention refers to a yeast culture used to initiate alcoholic fermentation during the brewing process; it can be understood as "yeast seed" or "fermentation starter." In the brewing of rice wine, baijiu, and sake, the starter culture is not directly usable dry yeast powder, but rather a specially cultivated liquid or solid culture containing a large number of highly active yeast cells. Its core function is to multiply the yeast to a sufficient scale and ensure it is in its strongest state before formal fermentation, so that fermentation can be started quickly and stably when put into large-scale production.

[0042] The "liquefying enzyme" mentioned in this invention refers to the common name of α-amylase, which is one of the most critical types of amylases in brewing, sugar making, and food processing. Its core function is to rapidly break down the long chains of starch molecules into short-chain dextrins, causing the starch gelatinized liquid to quickly "thin out" (viscosity decrease), hence the name "liquefaction".

[0043] The "saccharifying enzyme" mentioned in this invention refers to glucoamylase (also known as γ-amylase), which is the most crucial enzyme in the starch saccharification process. In the production of baijiu, beer, vodka, and fuel ethanol, the saccharifying enzyme converts the starch in raw materials (corn, sorghum, rice) into glucose, which then allows yeast to ferment and produce alcohol.

[0044] The "off-flavor" of rice wine as described in this invention refers to an unpleasant or abnormal odor or taste in rice wine. It is one of the core indicators for judging the quality of rice wine; any sensory characteristics deviating from the typical flavor of the product can be classified as an "off-flavor." Specifically, this invention includes p-2-methyltetrahydrothiophene and 4-vinylguaiacol.

[0045] The "aroma" referred to in this invention refers to the complex, layered, and typical aroma of Shaoxing wine, composed of hundreds of trace flavor substances. It is one of the most crucial sensory indicators for evaluating the quality of Shaoxing wine. Specifically, this invention includes key aroma substances such as ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol.

[0046] Test method: (1) Sample pretreatment and physicochemical index detection: After each sample was stirred evenly, it was dispensed into centrifuge tubes and centrifuged at 8000 r / min for 15 min. The supernatant was taken to determine the alcohol content, reducing sugar, total acid and amino acid nitrogen, etc. Each group was repeated in 3 parallel trials (n=3).

[0047] (2) Detection of volatile flavor compounds: Take a 20 mL headspace vial, add 5 mL of wine sample and 2.5 g of NaCl, and add 10 μL of internal standard solution (2-octanol, 100 mg / L); adsorb at 50℃ for 50 min, desorb at 250℃ for 5 min; GC temperature program: hold at 40℃ for 3 min; increase temperature at 6℃ / min to 100℃, increase temperature at 10℃ / min to 230℃, and hold for 7 min. GC carrier gas: high-purity helium (>99.999%), splitless, flow rate 1.0 mL / min; TG-WAXMS column (30 m × 0.25 mm × 0.25 μm), GC injection temperature 250℃, MS electron energy 70 eV, MS ionization mode: EI; MS emission current: 50 μA; ion source temperature: 230℃, transfer line temperature: 250℃, scan range: 33–400 amu. SPME fibers are 50 / 30 μm × 1 cm PDMS / DVB / CAR. A result of "0" indicates no detection.

[0048] (3) Evaluation of synergistic effect: Based on the measured values ​​of each compound in the single-component scheme (schemes 1 to 3), the linear summation expected value Vexp was calculated according to the compounding ratio; the measured value of the compound was recorded as Vmix, with the unit being μg / L, and E=Vmix-Vexp and Erel=E / Vexp were calculated to quantify the non-additive effect of the compound wheat koji. E>0 or Erel>0 indicates synergistic enhancement, and E<0 indicates antagonism or inhibition.

[0049] Raw materials used in the examples: Glutinous rice; block koji, inoculated raw wheat koji and popped wheat koji (Source: Shanghai Jin Feng Winery Co., Ltd.).

[0050] brewing yeast ( Saccharomyces cerevisiae Jiangnan1# was deposited at the China Center for Type Culture Collection on May 13, 2021, with accession number CCTCCNO:M2021523, and has been published in the patent application document CN113621528A.

[0051] The liquefying enzyme was purchased from Beijing Solarbio Technology Co., Ltd.; product number A8750.

[0052] The saccharifying enzyme was purchased from Yuanye Biotechnology Co., Ltd.; product number S10017.

[0053] The material preparation formulas involved in the embodiments are shown in Table 1.

[0054] Table 10.5 kg system feed formulation

[0055] The wheat koji addition schemes involved in the embodiments are shown in Table 2.

[0056] Table 2. Wheat Truffle Dosage and Dosage

[0057] Example 1 The specific steps are as follows: (1) Preparation of rice saccharification liquid culture medium: Mix raw glutinous rice and water at a mass ratio of 1:4, add liquefying enzyme (2‰ based on the mass of raw rice) and saccharifying enzyme (1‰ based on the mass of raw rice), and add 15% of the raw rice mass of koji. Saccharify and liquefy at 60℃ for 4-6 h until the sugar content is ≥13 °Brix. After filtering to remove rice lees, dispense and sterilize at 115℃ for 20 min, and cool for later use.

[0058] (2) Preparation of yeast starter: The seed culture was prepared by using brewing yeast jiangnan1# (CCTCC NO:M 2021523); the yeast was inoculated into the saccharified culture medium prepared and sterilized in step (1) at a rate of 3% and cultured at 28℃ and 150 r / min for 36 h to obtain yeast starter.

[0059] (3) Soaking and steaming rice: Weigh out glutinous rice and soak it in water until it is fully saturated for 3-5 days. After soaking, drain the rice to obtain wet rice. Steam the wet rice for 20-30 minutes until the rice is cooked but not mushy and there is no white core in the rice grains. Let it cool until the rice temperature is below 60℃ before use.

[0060] (4) Feeding and fermentation: Feeding is carried out based on Table 1. 37.5 g each of raw wheat koji and popped wheat koji (1:1) are added according to scheme 6 in Table 2. After feeding, the feed is placed at 25℃ for pre-fermentation for 5 days. The plastic wrap is punched with holes and the rake is opened every morning and evening. After the pre-fermentation is completed, the temperature is lowered to 15℃ for post-fermentation for 15 days. Samples are collected after fermentation.

[0061] Example 2 According to Scheme 7 in Table 2, add 25 g each of block koji, raw wheat koji and popped wheat koji (1:1:1), and the remaining steps and conditions are the same as in Example 1.

[0062] Example 3 According to Scheme 4 in Table 2, add 37.5 g of block koji and 37.5 g of raw wheat koji (1:1), and the remaining steps and conditions are the same as in Example 1.

[0063] Example 4 Add 37.5 g each of block koji and popcorn koji (1:1) according to scheme 4 in Table 2, and the remaining steps and conditions are the same as in Example 1.

[0064] Comparative Example 1 According to Scheme 1 in Table 2, use 75 g of block koji alone, and the remaining steps and conditions are the same as in Example 1.

[0065] Comparative Example 2 According to Scheme 2 in Table 2, use 75 g of raw wheat koji as the sole inoculator, and the remaining steps and conditions are the same as in Example 1.

[0066] Comparative Example 3 According to Scheme 3 in Table 2, use 75 g of popcorn koji alone, and the remaining steps and conditions are the same as in Example 1.

[0067] Test case 1. Physicochemical index testing After the fermentation of Examples 1-4 and Comparative Examples 1-3, the physicochemical properties were tested, and the results are shown in Table 3.

[0068] Table 3. Physicochemical index results after fermentation (mean ± standard deviation, n=3)

[0069] 2. Detection of volatile flavor compounds To demonstrate the combined aroma-enhancing and odor-controlling effects of compound malt koji, ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol were selected as key aroma-enhancing indicators (Table A), and 2-methyltetrahydrothiophene and 4-vinylguaiacol were selected as characteristic substance indicators (Table B). The Vmix, Vexp, synergy E, and relative synergy Erel of different compounding schemes (Schemes 4–7) are shown in Tables 4–12.

[0070] Table 4 Measured values ​​of relevant substances in Scheme 1, Scheme 2, and Scheme 3

[0071] Table 5 Synergistic Results of Key Flavoring Substances in Scheme 4 (Example 3)

[0072] Table 6 Synergistic Results of Key Flavoring Substances in Scheme 5 (Example 4)

[0073] Table 7 Synergistic Results of Key Flavoring Substances in Scheme 6 (Example 1)

[0074] Table 8 Synergistic Results of Key Flavoring Substances in Scheme 7 (Example 2)

[0075] Table 9 Synergistic Results of Key Characteristic Substances in Scheme 4 (Example 3)

[0076] Table 10 Synergistic Results of Key Characteristic Substances in Scheme 5 (Example 4)

[0077] Table 11 Synergistic Results of Key Characteristic Substances in Scheme 6 (Example 1)

[0078] Table 12 Synergistic Results of Key Characteristic Substances in Scheme 7 (Example 2)

[0079] Flavor enhancement effect: Under the condition of constant total amount of koji, Scheme 6 (1:1 mixture of raw wheat koji and popped wheat koji) showed significant positive synergy with ethyl acetate, ethyl octanoate, ethyl decanoate and phenylethanol (Erel was positive and the amplitude was large), indicating that the mixture can produce non-additive gain in the formation of fruit aroma ethyl ester and flower aroma alcohol; Scheme 4 and Scheme 7 showed moderate positive synergy, while Scheme 5 had a smaller synergistic amplitude.

[0080] Odor control effect: Scheme 7 (1:1:1 compound of three kojis) showed a significant negative synergy with 2-methyltetrahydrothiophene and 4-vinylguaiacol (E or Erel was negative). Among them, 2-methyltetrahydrothiophene could be inhibited to undetectable or significantly reduced, indicating that the equal ratio of three kojis can reduce the risk of sulfur / phenolic odor characteristics and improve aroma harmony.

[0081] Fermentation consistency: The alcohol content, reducing sugar, total acid and amino acid nitrogen of each scheme were in similar ranges (Table 3), indicating that the synergistic differences mainly came from the influence of the koji variety and its combination on metabolic distribution, rather than fermentation failure or differences in fermentation degree.

[0082] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for brewing rice wine, characterized in that, The method includes the following steps: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is a combination of two or three of the following: block yeast, inoculated raw wheat yeast and popped wheat yeast. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

2. The method according to claim 1, characterized in that, In step (1), the rice saccharification liquid culture medium is prepared by mixing raw glutinous rice and water at a mass ratio of 1:4, adding 2‰ liquefying enzyme and 1‰ saccharifying enzyme based on the mass of raw rice, and adding 10% to 15% of the raw rice mass of koji. The mixture is saccharified and liquefied at 55℃ to 65℃ for 4 to 6 hours until the sugar content is ≥13 °Brix. After filtration, it is sterilized at 115℃ for 20 minutes.

3. The method according to claim 1, characterized in that, In step (1), the brewing yeast jiangnan1# was inoculated into rice saccharification liquid culture medium at an inoculation rate of 3%, and cultured at 28℃ and 150 r / min for 36 h to obtain the yeast starter. The preservation number of the brewing yeast jiangnan1# is CCTCC NO:M 2021523.

4. The method according to claim 1, characterized in that, In step (2), the total amount of yeast added is 10% to 20% of the mass of glutinous rice; the amount of cooked glutinous rice is 100% to 200% of the mass of glutinous rice; the amount of water added is 80% to 160% of the mass of glutinous rice; and the amount of yeast added is 5% to 20% of the mass of glutinous rice.

5. The method according to claim 1, characterized in that, In step (2), raw wheat koji and popped wheat koji are mixed in a 1:1 ratio; or block koji, raw wheat koji and popped wheat koji are mixed in a 1:1:1 ratio.

6. A method for enhancing the aroma of rice wine, characterized in that, The method involves adding wheat koji during the brewing process of rice wine, which is prepared by mixing raw wheat koji and popped wheat koji in a 1:1 ratio.

7. The method according to claim 6, characterized in that, The flavor compounds that produce the aroma include ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol.

8. The method according to claim 6 or 7, characterized in that, Includes the following steps: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is prepared by mixing raw wheat yeast and popped wheat yeast in a 1:1 ratio. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

9. A method for reducing off-flavors in rice wine while maintaining aroma harmony, characterized in that, The method involves adding wheat koji during the brewing process of rice wine, which is prepared by compounding block koji, inoculated raw wheat koji, and popped wheat koji in a 1:1:1 ratio.

10. The method according to claim 9, characterized in that, The compounds that produce the odor include 2-methyltetrahydrothiophene and 4-vinylguaiacol.

11. The method according to claim 9 or 10, characterized in that, Includes the following steps: (1) Preparation of yeast starter: Prepare and sterilize rice saccharification liquid culture medium, inoculate it with brewing yeast and culture to obtain yeast starter; (2) Feeding and adding yeast: Glutinous rice, cooked glutinous rice, water and the yeast from step (1) are used as raw materials for feeding. Wheat yeast is added under the condition that the total amount of yeast is constant. The wheat yeast is prepared by mixing block yeast, inoculated raw wheat yeast and popped wheat yeast in a ratio of 1:1:

1. (3) Fermentation: Pre-fermentation and post-fermentation are carried out within the set temperature and time window; wherein, the temperature of pre-fermentation is 20℃~30℃ and the time is 3~7 days; the temperature of post-fermentation is 10℃~20℃ and the time is 10~30 days.

12. The application of the method according to any one of claims 1 to 5 in improving the flavor and quality of rice wine.

13. The application according to claim 12, characterized in that, The improvement of rice wine quality includes: (1) increasing aroma substances including ethyl acetate, ethyl octanoate, ethyl decanoate, and phenylethanol; and (2) inhibiting the characteristic substances of 2-methyltetrahydrothiophene and 4-vinylguaiacol, thereby controlling off-flavors and improving aroma harmony.

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