Sweet rice wine with improved flavor by low-temperature fermentation and brewing method thereof

Abstract

This invention discloses a method for improving the flavor of sweet rice wine through low-temperature fermentation and its brewing technique, relating to the field of winemaking technology. First, a short-term temperature increase (28-30℃) is implemented in the early stages of fermentation to create an optimal environment for efficient saccharification and flavor precursor accumulation in Rhizopus. Subsequently, a low-temperature stage (15-20℃) is initiated, under which slow primary fermentation and flavor maturation, primarily driven by yeast, take place. The "staged temperature-increase saccharification + low-temperature fermentation" process provided by this invention does not rely on psychrophilic strains or exogenous enzyme additives; it can be achieved through optimization of process parameters. This method not only successfully solves the core problem of insufficient saccharification kinetics at low temperatures, ensuring the smooth progress of the fermentation process, but also significantly improves the sensory quality of the final sweet rice wine (more complex and harmonious flavor), as well as the content of umami and sweet amino acids. Furthermore, this process is highly controllable and suitable for large-scale production, providing a novel technological path for the green and efficient brewing of high-quality sweet rice wine.

Description

Technical Field

[0001] This invention relates to the field of brewing technology, and in particular to a sweet rice wine with flavor-enhancing low-temperature fermentation and its brewing method. Background Technology

[0002] Sweet rice wine (CSRW) is a traditional Chinese alcoholic beverage favored by consumers for its unique flavor, low alcohol content, and high nutritional value. It is rich in oligosaccharides, peptides, amino acids, vitamins, and minerals, offering numerous health benefits, including antioxidant effects, blood sugar and cholesterol reduction, antihypertensive effects, immune enhancement, and improved gut health.

[0003] Temperature control is a common process in the brewing industry, as temperature plays a dominant role in the brewing process. Traditional sweet rice wine brewing typically involves fermentation at room temperature; however, brewing techniques must be continuously optimized to create diverse styles of sweet rice wine and meet consumer expectations. Low-temperature fermentation is widely believed to increase and retain more aroma compounds, improving the aroma of fermented wines, and is often used in the production of beer, Japanese sake, and white wine. However, there are still some technical bottlenecks to overcome in low-temperature fermentation processes. Specifically, Rhizopus grows and produces very little enzyme activity at low temperatures, failing to effectively colonize the substrate. This not only causes uneven saccharification but also results in the loss of the ability to build physical barriers to isolate contaminating microorganisms. More importantly, low temperatures significantly inhibit the activity of α-amylase and saccharifying enzymes, making starch saccharification the absolute bottleneck in the entire fermentation process, leading to a severe shortage of fermentable sugars and preventing yeast from carrying out normal alcoholic fermentation. At the same time, the primary metabolism of Rhizopus is also severely imbalanced, with insufficient production of organic acids, making it difficult to quickly establish the acidic environment required for antibacterial activity; the production of flavor precursors (amino acids, small peptides) is reduced; and its own weak alcoholic fermentation ability is basically lost at low temperatures, resulting in a lack of alcohol protection barrier in the early fermentation system. Summary of the Invention

[0004] The present invention aims to provide a sweet rice wine with improved flavor through low-temperature fermentation and its brewing method, in order to solve the problem that Rhizopus grows and produces enzymes with extremely low activity at low temperatures, making it unable to effectively colonize the substrate, resulting not only in uneven saccharification but also in the loss of the ability to build a physical barrier to isolate other microorganisms.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for brewing sweet rice wine with improved flavor through low-temperature fermentation, characterized by the following steps:

[0007] S1. Soak glutinous rice in water until the grains can be easily broken with your fingers and have no white center;

[0008] S2. Drain the soaked rice, steam for 30-40 minutes, and then quickly cool to 32-35°C.

[0009] S3. Inoculate with commercial pure culture of Rhizopus, add sterile water and stir well, put into a fermenter, and ferment at 28-30 °C for 24-36 h.

[0010] S4. Inoculate the obtained fermentation material with yeast and ferment at 15-20 °C for 3-7 days to obtain the crude fermented sweet rice wine.

[0011] S5. Sterilize the fermented crude product in a 75 °C water bath for 15 min to obtain the finished sweet rice wine.

[0012] A second aspect of the present invention provides a sweet rice wine prepared according to the brewing method described above.

[0013] The principle and beneficial effects of this technical solution:

[0014] This method offers an innovative dynamic temperature-controlled fermentation process. The core of this approach lies in precisely separating the optimal temperature windows for Rhizopus and yeast over time. First, a short-term temperature increase (28-30℃) is implemented at the initial stage of fermentation to create an optimal environment for efficient saccharification and flavor precursor accumulation in Rhizopus. Subsequently, a transition to a low-temperature stage (15-20℃) is initiated, under which yeast-dominated slow primary fermentation and flavor maturation take place. This strategy cleverly avoids the low-temperature limitations of Rhizopus while fully utilizing the regulatory advantages of low temperatures on yeast metabolism (such as promoting ester synthesis and inhibiting higher alcohol formation).

[0015] Compared to traditional constant-temperature fermentation or simply low-temperature fermentation throughout, the "staged warming saccharification + low-temperature fermentation" process provided by this invention does not rely on psychrophilic microorganisms or exogenous enzyme additives; it can be achieved through optimization of process parameters. This method not only successfully solves the core problem of insufficient saccharification kinetics at low temperatures, ensuring the smooth progress of the fermentation process, but also significantly improves the sensory quality of the final sweet rice wine (more complex and harmonious flavor), organic acid content, and antioxidant activity. Furthermore, this process is highly controllable and suitable for large-scale production, providing a new technological path for the green and efficient brewing of high-quality sweet rice wine. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the total amount of amino acids. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0018] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, or step, but does not exclude the presence or addition of one or more other features, elements, or steps.

[0019] A method for brewing sweet rice wine with improved flavor through low-temperature fermentation achieves a stable and efficient fermentation process under low-temperature conditions, significantly enhancing the product's taste and quality. The fermentation process is optimized, overcoming the core technical bottleneck of insufficient Rhizopus saccharification activity in traditional low-temperature fermentation. This avoids the risk of microbial ecological imbalance due to the reliance on exogenous additives and simplifies the control of the fermentation process. The process system comprises three core stages: rice processing, staged temperature-increase saccharification, and low-temperature primary fermentation. Through precise temporal temperature control, the optimal conditions for the interaction of Rhizopus and yeast are separated over time.

[0020] The specific steps are as follows:

[0021] 1. Soak 200g of glutinous rice in water for 8 hours.

[0022] 2. Drain the soaked rice, steam for 40 minutes, and then quickly cool to 32°C.

[0023] 3. Inoculate with commercial pure culture Rhizopus at 0.4% of the glutinous rice (dry basis by weight of glutinous rice), add 300mL of sterile water, stir well, put into a fermentation tank, and ferment at 30 °C for 36 h.

[0024] 4. Inoculate the obtained fermentation material with 1 × 10 6 CFU / g yeast, fermented at 20 °C for 5 days, yields crude fermented sweet rice wine.

[0025] 5. Sterilize the fermented crude product in a 75 °C water bath for 15 min to obtain the finished sweet rice wine.

[0026] Effect evaluation

[0027] I. Sensory Evaluation

[0028] Table 1 shows the sensory scoring criteria, and Table 2 shows the sensory evaluation of each brewing method: Method 1 is the traditional method for brewing sweet rice wine, and Method 2 is the method of this invention for brewing sweet rice wine. The sensory scores in Table 2 are the average scores obtained from blind taste tests of the samples by 10 tasters. It can be seen that the sensory scores of the sweet rice wine brewed by this method (Method 2) are significantly better than those of the traditional method (Method 1) in terms of aroma, taste, and overall harmony.

[0029] Table 1

[0030]

[0031] Table 2

[0032]

[0033] II. Physicochemical Indicators

[0034] Table 3 shows the statistical table of physicochemical indicators of sweet rice wine. The results show that the sweet rice wine produced by the method of the present invention (method 2) maintains similar pH, soluble solids, and total sugar levels as the sweet rice wine produced by the traditional method (method 1). At the same time, the total acid content is significantly reduced, from 6.52 g / L to 4.40 g / L, resulting in a smoother and more refreshing taste with a more balanced acidity.

[0035] Table 3

[0036]

[0037] III. Amino Acid Content

[0038] Quantitative analysis of free amino acids in sweet rice wine produced by the two methods was performed, and the results are shown in Table 4. Figure 1 As shown. It can be seen that the sweet rice wine brewed by the method (method 2) of the present invention contains:

[0039] 1. Optimization of flavor amino acids: The total amount of umami amino acids increased from 22.28 ng / µL to 24.27 ng / µL; the total amount of sweet amino acids increased significantly from 59.89 ng / µL to 66.37 ng / µL, which is highly consistent with the results of better "taste" and "overall harmony" in the sensory evaluation.

[0040] 2. Significant reduction in bitter amino acids: The total amount of bitter amino acids, which are the main source of bitterness in the wine, has decreased significantly from 145.65 ng / µL to 103.42 ng / µL, effectively eliminating the aftertaste that may exist in traditional rice wine and improving the drinking comfort and the purity of flavor.

[0041] Table 4

[0042]

[0043] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0044] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the embodiments of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for brewing sweet rice wine with improved flavor through low-temperature fermentation, characterized in that, Includes the following steps: S1. Soak glutinous rice in water until the grains can be easily broken with your fingers and have no white center; S2. Drain the soaked rice, steam for 30-40 minutes, and then quickly cool to 32-35°C. S3. Inoculate with commercial pure culture of Rhizopus, add sterile water and stir well, put into a fermenter, and ferment at 28-30 °C for 24-36 hours. S4. Inoculate the obtained fermentation material with yeast and ferment at 15-20 °C for 3-7 days to obtain the crude fermented sweet rice wine. S5. Sterilize the fermented crude product in a 75 °C water bath for 15 min to obtain the finished sweet rice wine.

2. A sweet rice wine prepared according to the brewing method of claim 1.

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