High-temperature daqu brewing rice wine process and flavor optimization method thereof

Abstract

This invention discloses a high-temperature Daqu (large koji) brewing process for rice wine and its flavor optimization method in the field of rice wine brewing technology. Using glutinous rice as raw material, it employs a traditional semi-solid fermentation process, using a special high-temperature Daqu for sauce-flavored baijiu as the saccharification and fermentation agent to replace traditional wheat koji. By precisely controlling key process parameters such as soaking, steaming, saccharification, and constant-temperature fermentation, and monitoring changes in physicochemical indicators such as temperature, reducing sugar, pH, and total acid during fermentation, high-quality rice wine is ultimately produced. Compared with wheat koji rice wine, the high-temperature Daqu rice wine produced by this invention has an alcohol content of 9.4% vol, with 22 volatile flavor compounds detected, mainly isoamyl formate and phenylethyl alcohol. It has a high ester content, no acid or ketone substances, and very few off-flavors. The wine is clear and slightly yellow, smooth on the palate, and has an elegant flavor, with a sensory score significantly higher than traditional wheat koji rice wine.

Description

Technical Field

[0001] This invention relates to the field of rice wine brewing technology, and in particular to a process for brewing rice wine with high-temperature daqu (a type of starter culture) and its flavor optimization method. Background Technology

[0002] Rice wine is a traditional low-alcohol fermented beverage in my country with a long history, a sweet taste, and rich nutrition. It is a common drink for daily consumption and banquets. Traditional rice wine brewing often uses wheat koji, sweet wine koji, and industrial yeast as saccharification and fermentation agents, which results in problems such as a single flavor, insufficient complexity, and a tendency to produce off-flavors.

[0003] High-temperature Daqu is the core saccharification and fermentation agent for sauce-flavored Baijiu. It is made from wheat as raw material, through high-temperature koji making at 60℃ and storage for more than 6 months. It is rich in functional microorganisms such as Bacillus, Aspergillus, and Rhizopus, and has extremely strong ester and aroma production capabilities, which can endow the liquor with a rich, elegant, and pure complex aroma.

[0004] Currently, high-temperature Daqu (a type of starter culture) is only used in the production of Maotai-flavor liquor and has not yet been applied to rice wine brewing. Traditional wheat koji brewing of rice wine easily produces a large amount of isoamyl alcohol, resulting in a putrid odor that seriously affects sensory quality and product grade. Summary of the Invention

[0005] The present invention aims to provide a process for brewing rice wine with high-temperature Daqu (a type of starter culture) and a method for optimizing its flavor, so as to solve the problems of monotonous flavor, strong off-flavors, and narrow application range of starter culture in existing rice wine brewing processes.

[0006] The process for brewing rice wine using high-temperature Daqu (a type of starter culture) in this scheme includes the following steps: S1 Raw Material Soaking: Take glutinous rice and soak it in water for 10-14 hours until the water completely submerges the glutinous rice; S2 Steaming: Steam the soaked glutinous rice until cooked, adding water and stirring every 8-12 minutes during the steaming process; S3 Saccharification: Spread the steamed glutinous rice out to cool, add 60-70℃ purified water and 0.08%-0.12% saccharifying enzyme, and saccharify at 30-35℃ for 3-5 hours; S4 Fermentation: After saccharification, the temperature is lowered to 30-34℃, and 0.04%-0.06% yeast is added. After fermentation for 20-28 hours, high-temperature Daqu (a type of starter culture) is added, with the amount added being 2.5%-3.5% of the glutinous rice mass. The mixture is then fermented at a constant temperature of 30-32℃ for 5-7 days to obtain the finished rice wine.

[0007] Furthermore, the high-temperature koji is a special high-temperature koji for sauce-flavored baijiu, with a koji-making temperature of ≥60℃ and a storage period of ≥6 months.

[0008] Furthermore, the temperature was controlled at 25–32°C during fermentation, reaching a peak temperature of 30–32°C on the 4th day, and then gradually dropping back to room temperature in the later stages.

[0009] Furthermore, the reducing sugar content showed a continuous decreasing trend during the fermentation process, and after 5 to 7 days of fermentation, the reducing sugar content was close to 0 g / L.

[0010] Furthermore, the finished rice wine has an alcohol content of 9.2%–9.5% vol, a pH of 3.7–3.9, and a total acid content of 1.2–1.4 g / L.

[0011] Twenty-two volatile flavor compounds were detected in the finished rice wine, including eight alcohols and fourteen esters. No acids or ketones were detected. Among the volatile flavor compounds, the content of isoamyl formate was 260-270 μg / 100mL, and the content of phenylethanol was 130-135 μg / 100mL. The main aromas were mulberry and rose.

[0012] The working principle and beneficial effects of this scheme: The high-temperature koji for sauce aroma is made at a high temperature of over 60℃ and stored for a long time, which enriches a complex microbial system with Bacillus and functional Aspergillus as the core and a rich enzyme system. In the semi-solid fermentation process of rice wine, it can achieve targeted regulation of flavor through step-by-step synergistic action: the saccharifying enzyme and yeast first convert glutinous rice starch into fermentable sugar and initially produce alcohol. Then, the microorganisms and enzyme system in the high-temperature koji slowly metabolize and efficiently convert precursor substances such as sugar and amino acids into esters and higher alcohols, represented by isoamyl formate and phenylethanol. At the same time, it inhibits the growth and metabolism of bacteria that produce off-flavors and reduces the generation of undesirable substances such as isoamyl alcohol, forming a pure complex aroma system dominated by mulberry and rose aromas, which solves the defects of traditional rice wine that are prone to producing a putrid smell and lacking aroma layers.

[0013] This invention is the first to apply high-temperature Daqu (a type of starter culture) of soy sauce aroma to the field of rice wine brewing, breaking through the technical limitation that high-temperature Daqu is only used in the production of baijiu (Chinese liquor). Through the synergistic effect of step-by-step fermentation process and the functional characteristics of high-temperature Daqu, the resulting rice wine has a stable alcohol content of 9.2%-9.5% vol. The wine is clear and slightly yellow, with a smooth taste and a harmonious balance of sweet and sour. The content of ester flavor substances is significantly increased, and no acid or ketone impurities are detected. The aroma is pure and elegant, and the sensory quality is far superior to that of rice wine brewed with traditional wheat koji. The process parameters are controllable and highly repeatable, making it suitable for industrial production and development of high-end specialty rice wine products with broad market prospects.

[0014] A method for flavor optimization in high-temperature Daqu-brewed rice wine involves using high-temperature Daqu from Maotai-flavor baijiu as a saccharification and fermentation agent in a semi-solid fermentation process using glutinous rice as a substrate. This aims to enhance the aroma purity of the rice wine, reduce off-flavors, and optimize its taste. Attached Figure Description

[0015] Figure 1 A graph showing temperature changes during the fermentation process of rice mash; Figure 2 A graph showing the change in reducing sugar content during the fermentation process of rice mash; Figure 3 A comparison chart of alcohol content in the finished wine mash; Figure 4 A graph showing pH changes during the fermentation process of rice wine mash; Figure 5 A graph showing the change in total acid content during the fermentation process of rice mash; Figure 6 This is a comparison chart of alcohol concentrations; Figure 7 This is a comparison chart of ester compound concentrations; Figure 8 This is a comparison chart of acid compound concentrations; Figure 9 This is a comparison chart of ketone compound concentrations; Figure 10 This is a comparison chart of aldehyde compound concentrations. Detailed Implementation

[0016] The following detailed explanation illustrates the specific implementation methods: Example: High-temperature Daqu brewing of rice wine S1 Raw Material Soaking: Take glutinous rice and soak it in water for 12 hours, ensuring the water completely submerges the glutinous rice. S2 Steaming: Steam the soaked glutinous rice until cooked, adding water and stirring once every 10 minutes during the steaming process; S3 Saccharification: Spread the steamed glutinous rice out to cool, add 65℃ purified water and 0.1% saccharifying enzyme, and saccharify at 32℃ for 4 hours; S4 Fermentation: After saccharification, the temperature is lowered to 32℃, and 0.05% yeast is added. After fermentation for 24 hours, 3% of the weight of ground high-temperature koji (fermentation starter) of glutinous rice is added, and the mixture is fermented at a constant temperature of 32℃ for 6 days to obtain the finished rice wine. Figure 1 , Figure 2 , Figure 4 and Figure 5 ; S5 Finished Product Testing: After fermentation, the alcohol content was measured, and the results are shown in Figure 3. The content of volatile flavor substances, alcohols, esters, acids, ketones, and aldehydes were measured, and the results are shown in Figures 6, 7, 8, 9, and 10, respectively.

[0017] Comparative Example The same raw materials, soaking, steaming, saccharification, and yeast fermentation process as in the previous example were used, except that the high-temperature Daqu was replaced with an equal amount of wheat koji, and all other parameters and operating steps were the same. Temperature, reducing sugar, pH, and total acid were monitored daily during the fermentation process, and the results are shown in Figures 1, 2, 4, and 5, respectively; the alcohol content of the finished product is shown in Figure 3; and the contents of alcohols, esters, acids, ketones, and aldehydes in the volatile flavor compounds are shown in Figures 6, 7, 8, 9, and 10, respectively.

[0018] Table 1 Comparison of Key Indicators of Finished Fermented Wine Mash

[0019] The trends in physicochemical indicators of the examples and comparative examples were basically consistent, with alcohol contents of 9.4% vol and 9.2% vol, respectively, showing only minor differences. Flavor compound detection showed that the examples contained 22 volatile components, including 8 alcohols and 14 esters, with no detected acids or ketones. The aroma was dominated by isoamyl formate and phenylethanol, with prominent mulberry and rose notes, and no off-flavors. The comparative example contained 24 components, including 9 alcohols, 14 esters, and 1 acid, with a high isoamyl alcohol content and a noticeable putrid odor. Combined with sensory evaluation, the examples averaged 88 points, while the comparative example averaged 76 points. The process of this invention is significantly superior to traditional wheat-based rice wine in terms of aroma, taste, and quality.

[0020] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A process for brewing rice wine using high-temperature Daqu (a type of starter culture), characterized in that: Includes the following steps: S1 Raw Material Soaking: Take glutinous rice and soak it in water for 10-14 hours until the water completely submerges the glutinous rice; S2 Steaming: Steam the soaked glutinous rice until cooked, adding water and stirring every 8-12 minutes during the steaming process; S3 Saccharification: Spread the steamed glutinous rice out to cool, add 60-70℃ purified water and 0.08%-0.12% saccharifying enzyme, and saccharify at 30-35℃ for 3-5 hours; S4 Fermentation: After saccharification, the temperature is lowered to 30-34℃, and 0.04%-0.06% yeast is added. After fermentation for 20-28 hours, high-temperature Daqu (a type of starter culture) is added, with the amount added being 2.5%-3.5% of the glutinous rice mass. The mixture is then fermented at a constant temperature of 30-32℃ for 5-7 days to obtain the finished rice wine.

2. The process for brewing rice wine with high-temperature Daqu (a type of starter culture) according to claim 1, characterized in that: The high-temperature koji is a special high-temperature koji for sauce-flavored baijiu, with a koji-making temperature of ≥60℃ and a storage period of ≥6 months.

3. The process for brewing rice wine with high-temperature Daqu (a type of starter culture) according to claim 2, characterized in that: During fermentation, the temperature was controlled at 25-32℃, reaching a peak temperature of 30-32℃ on the 4th day, and then gradually dropping back to room temperature.

4. The process for brewing rice wine with high-temperature Daqu (a type of starter culture) according to claim 3, characterized in that: The reducing sugar content showed a continuous decreasing trend during fermentation, and approached 0 g / L after 5-7 days of fermentation.

5. The process for brewing rice wine with high-temperature Daqu (a type of starter culture) according to claim 4, characterized in that: The finished rice wine has an alcohol content of 9.2%–9.5% vol, a pH of 3.7–3.9, and a total acid content of 1.2–1.4 g / L.

6. The method for flavor optimization of rice wine according to any one of claims 1 to 5, characterized in that: High-temperature Daqu (a type of starter culture) of soy sauce-flavored baijiu is used as a saccharification and fermentation agent in the semi-solid fermentation of glutinous rice-based liquor.

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