Fermentation process of rice wine soda water and product thereof

Abstract

The invention discloses a fermentation process of rice wine soda water and a product thereof, and particularly relates to the technical field of fermented beverage processing. The process mainly comprises the steps of fermentation substrate preparation, two-stage temperature control fermentation, membrane filtration sterilization, carbonation treatment and the like. By adopting a rice wine koji and wine yeast staged fermentation technology and combining an accurate temperature control system and a membrane filtration carbonation integrated process, stepped conversion of sugar and stable dissolution of carbon dioxide are realized. The product has the characteristics of controllable alcohol content, good bubble durability, coordinated and stable flavor and the like. The method effectively solves the technical problems of large residual sugar amount fluctuation, unstable carbonation, unbalanced flavor and the like in the traditional process, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of fermented beverage processing technology, and more specifically, to a fermentation process for rice wine soda and its product. Background Technology

[0002] Rice wine soda, a product combining traditional fermented beverages and modern carbonated drinks, has gradually gained attention in the beverage market in recent years. Its development has evolved from small-scale family workshops to industrialized manufacturing, with production processes progressing from single-strain rice wine fermentation to a complex fermentation technology system. Industry trends show that between 2015 and 2022, the annual growth rate of this type of product remained between 8% and 12%, with production technology focusing on low-temperature fermentation, strain selection, and flavor control. Currently, mainstream processes often employ a late-stage mixing of rice wine and carbonated beverages, or fermentation using a single yeast strain to produce gas. The production process is gradually incorporating modern technologies and equipment such as temperature control and aseptic filling.

[0003] The existing technology has several obvious shortcomings: First, most production processes adopt a single-stage fermentation method, resulting in insufficient sugar conversion, with residual sugar content fluctuating between 3 and 8 grams per liter, and a simple flavor composition. Second, the carbonation process mostly uses the direct injection method, resulting in insufficient integration of carbon dioxide with the wine, poor bubble stability, and a pressure decay rate of 25% to 40% after 30 minutes. Third, traditional processes lack precision in controlling fermentation temperature, with fluctuations often exceeding ±2 degrees Celsius, leading to inconsistent yeast metabolites and batch-to-batch quality differences. Finally, the existing technology lacks an effective flavor coordination mechanism, resulting in an imbalance in the ratio of organic acids to esters, which can easily lead to problems such as an unbalanced sweet and sour taste or a bitter aftertaste.

[0004] Therefore, a fermentation process and product for rice wine soda are proposed to address the above-mentioned problems. The following technical issues are specifically addressed: how to achieve a stepwise conversion and precise control of sugar content; how to improve the solubility and stability of carbon dioxide in the liquor; how to improve the temperature control precision and consistency of metabolites during fermentation; and how to coordinate the composition ratio and presentation of various flavor compounds. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a fermentation process for rice wine soda and its product, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a fermentation process for rice wine soda, the process comprising the following steps:

[0007] S1. Prepare fermentation substrate: Soak and steam glutinous rice to obtain cooked rice material. Mix cooked rice material with purified water and add sugar source to form initial fermentation substrate. Sugar source includes white sugar and maltose, and the mass ratio of white sugar to maltose is 3:1 to 5:1.

[0008] S2. Carry out the first stage of fermentation. Add rice wine koji to the initial fermentation substrate and stir evenly. Ferment in a closed container at a temperature of 25 degrees Celsius to 30 degrees Celsius for 3 to 5 days to obtain primary rice wine mash.

[0009] S3. The second stage of fermentation is carried out by pressing and filtering the primary rice wine mash to obtain the clear liquid. Sucrose syrup is added to the clear liquid and wine yeast is inoculated. The amount of sucrose syrup added is 5% to 8% of the mass of the clear liquid, and the amount of wine yeast inoculated is 0.5 to 1.5 grams per liter of clear liquid. The mixture is fermented in a closed system at a temperature of 18 to 22 degrees Celsius for 5 to 7 days to obtain the secondary fermentation liquid.

[0010] S4. To terminate and fill the fermentation, the secondary fermentation liquid is cooled to below 4 degrees Celsius to terminate the fermentation activity. After being sterilized by membrane filtration, it is introduced into a pressurized container for carbonation treatment and finally bottled to obtain the finished rice wine soda.

[0011] Optionally, in the process of preparing the fermentation substrate, the glutinous rice is soaked for 4 to 6 hours, the cooking pressure is 0.1 MPa to 0.15 MPa, and the cooking time is 25 to 35 minutes; the mass ratio of the cooked rice to purified water is 1:2 to 1:3.

[0012] Optionally, in the first stage of fermentation, the amount of rice wine starter inoculated is 0.8% to 1.2% of the total mass of the initial fermentation substrate; the relative humidity of the closed fermentation environment is controlled between 75% and 85%.

[0013] Optionally, in the second stage of fermentation, the pressure filtration process is carried out using a plate and frame filter press at an operating pressure of 0.4 MPa to 0.6 MPa; the wine yeast strain is activated dry yeast, which is rehydrated for 15 minutes at 35 degrees Celsius with warm water at a weight ratio of 1:10 before use.

[0014] Optionally, during the termination and filling process, the membrane filtration sterilization uses a polyethersulfone filter membrane with a pore size of 0.45 micrometers; the carbonation treatment is carried out by introducing carbon dioxide gas into a pressurized container at a temperature of 0 to 4 degrees Celsius to maintain the pressure at 0.2 MPa to 0.3 MPa for 30 minutes.

[0015] Optionally, the process further includes adding a flavor modifier to the secondary fermentation broth after the second stage of fermentation is completed and before termination and filling. The flavor modifier comprises citric acid and ascorbic acid, wherein the amount of citric acid added is 0.05% to 0.1% of the mass of the secondary fermentation broth, and the amount of ascorbic acid added is 0.01% to 0.02% of the mass of the secondary fermentation broth.

[0016] A rice wine soda product comprising alcoholic components produced by two-stage fermentation of glutinous rice, carbon dioxide gas introduced by yeast fermentation and carbonation treatment, and unconsumed sugar; wherein the alcoholic components are present in a volume percentage of 0.8% to 2.5%, and the carbon dioxide gas is present in a pressure of 0.15 MPa to 0.25 MPa at 20 degrees Celsius.

[0017] Optionally, the product also contains citric acid and ascorbic acid from flavor modifiers, with citric acid content ranging from 200 mg / L to 500 mg / L and ascorbic acid content ranging from 50 mg / L to 100 mg / L.

[0018] Optionally, the product has a sugar content ranging from 5 g / L to 15 g / L, and the sugar composition includes residual maltose, sucrose, and glucose and fructose produced during fermentation.

[0019] Optionally, the product can be stored for at least 90 days in sealed packaging at an ambient temperature of 4 to 25 degrees Celsius without the addition of any artificial preservatives.

[0020] The technical effects and advantages of this invention are as follows:

[0021] Compared to existing technologies, this invention achieves stepwise conversion and precise control of sugar content through a two-stage fermentation process. Specifically, the first stage uses rice wine koji for saccharification and alcoholic fermentation, while the second stage introduces wine yeast for gas-producing fermentation. The two stages are controlled at different temperature ranges of 25 to 30 degrees Celsius and 18 to 22 degrees Celsius, respectively, and the fermentation time is dynamically adjusted by monitoring sugar content changes in real time. This segmented control method keeps the residual sugar content stably controlled within the range of 5 to 15 grams per liter, while effectively improving sugar utilization and avoiding the problems of insufficient sugar conversion or over-fermentation common in single fermentation processes, resulting in a more stable and moderate sweetness in the product.

[0022] Compared to existing technologies, this invention improves the stability of carbon dioxide dissolution by introducing an integrated membrane filtration and carbonation system. Specifically, a polyethersulfone filter membrane with a pore size of 0.45 micrometers is sterilized under low-temperature conditions, and then gas-liquid mass transfer is carried out in a vertical packed tower by controlling the pressure range of 0.2 to 0.3 MPa and the temperature conditions of 0 to 4 degrees Celsius. This treatment method results in carbon dioxide bubble particle size distribution in the range of 50 to 100 micrometers. The gas pressure decay rate of the product is less than 15% within 120 minutes after the product is turned on, and the bubble persistence is improved by about 2 times, thus improving the taste and sensory quality of the product.

[0023] Compared to existing technologies, this invention improves the precision of the fermentation process by establishing a multi-level temperature control system. It combines a coil-type heat exchange system with a microprocessor temperature control device to keep the temperature fluctuation within ±0.5 degrees Celsius throughout the fermentation process. At the same time, it collects key parameters such as temperature and pH value in real time through an online monitoring system. This control method improves the consistency of yeast metabolites by about 40%, and reduces the batch-to-batch alcohol content fluctuation range from the traditional ±1.2% to ±0.5%, effectively ensuring the stability and repeatability of product quality.

[0024] Compared to existing technologies, this invention optimizes the product's taste balance by constructing a flavor substance coordination mechanism. After fermentation, 0.05% to 0.1% citric acid and 0.01% to 0.02% ascorbic acid are added, and uniform dispersion is achieved using a static mixer. The product is then aged under inert gas protection. This treatment method controls the ratio of organic acids to esters within the optimal range, resulting in a golden ratio of 1:8 to 1:12 for the product's sweet and sour taste. This avoids undesirable flavor characteristics such as bitterness in the aftertaste and presents a fresh and harmonious taste. Attached Figure Description

[0025] Figure 1 This is a flowchart of the two-stage fermentation process for rice wine and soda of the present invention. Detailed Implementation

[0026] The following will refer to the appendices in the embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Implementation Process 1:

[0028] A fermentation process for rice wine soda, comprising the following steps:

[0029] In the stage of preparing fermentation substrate, glutinous rice raw materials with a fine whiteness that meet the standard need to be selected. After removing surface impurities through a mechanical cleaning device, the rice is transferred to a soaking tank. Countercurrent osmosis soaking technology is used to make the moisture content of the glutinous rice uniform to reach the predetermined standard. After soaking, the glutinous rice is drained and then transported to a continuous cooking equipment. By adjusting the steam pressure and material retention time, the glutinous rice is completely gelatinized. The degree of gelatinization needs to reach a specific index to facilitate the subsequent saccharification reaction.

[0030] Cooked rice and purified water treated by reverse osmosis are introduced into a mixing tank in proportion. A uniform suspension is formed by a stirrer. Then, a compound sugar source of white sugar and maltose, which is precisely proportioned by a metering system, is added. When adding the sugar source, the temperature of the mixture must be kept within a specific range to prevent sugar crystallization.

[0031] The first stage of fermentation is carried out in a fermentation tank with temperature control function. Before inoculation, the rice wine koji needs to be activated in advance. The activation process involves mixing the koji with sterile water in a specific ratio and culturing and activating the enzyme system under constant temperature conditions. After inoculation, the koji is evenly distributed by multiple layers of stirring blades in the tank. During fermentation, the temperature and pH changes in the tank are continuously monitored by sensors, and a micro-pressure control system is used to maintain the pressure in the tank within a specific range.

[0032] The second stage of fermentation begins with the solid-liquid separation process of the primary fermentation mash. A plate and frame filter press is used in conjunction with filter cloth of a specific pore size to achieve efficient separation. After the clear liquid is transferred to the secondary fermentation tank, the precise amount of sucrose syrup to be added is determined by an online sugar content detection system. After centrifugation and activation culture, the wine yeast is inoculated in suspension form. The secondary fermentation adopts a step-down cooling control strategy. During the fermentation process, sugar content conversion and alcohol production dynamics are sampled and monitored regularly.

[0033] The termination and filling stage first uses a plate heat exchanger to rapidly cool the fermentation broth to a predetermined temperature to inhibit yeast activity. Then, cross-flow filtration technology is used to remove microbial residues through a membrane module with a specific pore size. The filtrate enters a carbonation tower where it is mixed with food-grade carbon dioxide under specific pressure and temperature conditions. Finally, the product is packaged through an aseptic filling line.

[0034] In the preparation of the fermentation substrate, the glutinous rice soaking process employs multi-stage temperature control technology. A higher temperature is used initially to promote water penetration, while the temperature is lowered later to prevent nutrient loss. Changes in water conductivity are continuously monitored during soaking to determine the degree of soaking. The cooking process uses a gradual pressure change operation. An initial low-pressure stage allows the glutinous rice particles to expand slowly, followed by a step-by-step pressure increase to completely break down the crystal structure. After cooking, a vacuum cooling system is used to rapidly reduce the rice temperature to prevent surface crusting. The mixing of the cooked rice and purified water is achieved using a turbine mixer at a specific speed to form a homogeneous system.

[0035] During the mixing process, the viscosity of the mixture is monitored in real time by an online viscometer, and the stirring intensity and mixing time are dynamically adjusted according to the monitoring data. The sugar source addition system is equipped with a heating and melting device and a precision metering pump to ensure that the sugar solution is injected into the mixing tank at a constant flow rate within a specific temperature range. The injection point is set at the center of the vortex of the stirrer to achieve rapid dispersion.

[0036] In the first stage of fermentation, the activation of rice wine koji adopts a three-stage expansion process: first, the original koji and sterilized wheat bran culture medium are cultured under specific humidity conditions to expand the number of microorganisms, then transferred to liquid culture medium for enzyme activation, and finally the accumulation of metabolites is completed through an airlift fermenter; the inoculation operation is carried out in a sterile positive pressure environment, and the inoculation pipeline adopts a steam sterilization system to ensure no contamination by other microorganisms;

[0037] The fermenter is equipped with multiple sets of coil-type heat exchange systems, which precisely control the fermentation temperature by adjusting the flow rate of the cooling medium. The tank is equipped with multiple layers of radial flow stirring blades, and the blade angles are specially designed to achieve fluid circulation throughout the tank. During the fermentation process, an online gas chromatography system is used to monitor the generation of volatile metabolites, while an automatic pH compensation system is used to maintain a stable acid-base environment.

[0038] In the second stage of fermentation, the filtration process uses a diaphragm plate and frame filter press. In the early stage of filtration, a constant flow operation mode is used, and in the later stage, it is switched to a constant pressure operation mode to improve the filtrate yield. The filter cloth is selected with a specific material and weaving method to balance filtration efficiency and turbidity control. In the process of clear liquid transfer, carbon dioxide is used to cover and protect against oxidation, and the conveying pipeline is insulated throughout to avoid temperature fluctuations.

[0039] The sucrose syrup is pasteurized before being added, and the sugar concentration is corrected in real time using an online refractometer. The wine yeast reactivation process uses a programmed temperature control device, and a specific ratio of nitrogen source and mineral elements is added to the reactivation solution to promote yeast activation. After inoculation, the cells are evenly dispersed through a distributor at the bottom of the tank. The secondary fermenter is equipped with a micro dissolved oxygen probe and an oxidation-reduction potential sensor, which automatically adjusts the stirring rate and jacket cooling intensity based on the monitoring data.

[0040] During the termination and filling process, the cooling process adopts a three-stage plate heat exchange system: the first stage uses chilled water for initial cooling, the second stage uses ethylene glycol solution for deep cooling, and the third stage uses a liquid nitrogen injection device to achieve the final temperature target; the membrane filtration system includes two-stage modules: pre-filtration and sterilization filtration. Pre-filtration uses deep filter cotton cores to remove larger particles, and sterilization filtration uses a pleated filter membrane structure to ensure that the microbial rejection rate meets the standards.

[0041] The carbonation process takes place in a vertical packed tower. Carbon dioxide gas is introduced from the bottom of the tower through a pressure reducing valve and a flow controller, while liquid forms a uniform liquid film through a spray device at the top of the tower. Mass transfer occurs between the gas and liquid phases on the surface of the packing. The filling line is equipped with an electronic weighing system and a laser detection device to ensure that the capacity and sealing of each bottle meet the predetermined standards.

[0042] The process also includes a flavor adjustment section after the second stage of fermentation and before termination and filling: citric acid is added by dissolving the crystalline solid in sterile water and injecting it into the pipeline mixer through a metering pump. The addition point is set in front of the plate heat exchanger to achieve rapid mixing by utilizing fluid turbulence.

[0043] The ascorbic acid solution was prepared in an inert gas protected environment. The preparation tank was filled with nitrogen to prevent oxidation and failure. The addition system used light-proof pipes and amber-colored storage tanks to reduce photosensitivity. After the flavor modifier was injected, it was dispersed in multiple stages through a static mixer and then entered a retention tank for short-term aging to fully integrate the flavor components. During the aging process, the tank was kept at a low temperature and gentle stirring was applied.

[0044] The alcohol content of this product comes from the fermentation products of glutinous rice starch after enzymatic decomposition, including ethanol and trace amounts of higher alcohols; carbon dioxide gas is obtained through a dual process of secondary fermentation and external injection, forming a delicate and persistent bubble structure; the sugar composition includes unfermented maltose and sucrose, as well as reducing sugars such as glucose and fructose produced during fermentation.

[0045] The product's colloidal system contains trace amounts of protein and polypeptides from glutinous rice, which form stable complexes with polysaccharides; the organic acid composition includes lactic acid and succinic acid produced during fermentation, as well as added citric acid, forming a sour flavor system; the volatile flavor compounds include a variety of compounds such as esters, aldehydes, and ketones, which together constitute the typical flavor characteristics.

[0046] Citric acid in this product exists in hydrated crystal form. It ionizes in solution to generate hydrogen ions, which participate in regulating acid-base balance and form soluble complexes with metal ions. The enol hydroxyl group in the ascorbic acid molecule provides reducing power and acts as an oxidative buffer in the product.

[0047] The ratio of the two acidulants is specifically designed to form a multi-layered acidity perception system together with the organic acids produced by fermentation; the added acidulants and residual sugars form a specific sugar-acid ratio, which affects the perceived intensity and persistence of the product flavor through synergistic taste effects.

[0048] In the sugar composition of this product, maltose and sucrose, as non-reducing sugars, provide basic sweetness and fullness; glucose and fructose, as reducing sugars, participate as precursors in the Maillard reaction; the proportions of various sugars are precisely adjusted through fermentation process control and post-fermentation blending to form a specific sweetness release curve; the hydroxyl groups in sugar molecules form a hydrogen bond network with water molecules, affecting the product's viscosity characteristics and mouthfeel; the types and proportions of unfermented sugars directly affect the product's osmotic pressure and microbial stability.

[0049] The product's stability stems from several technical factors: alcohol content and pH work together to form a microbial inhibition system; carbonic acid saturation creates an anaerobic environment that inhibits the growth of aerobic bacteria; membrane filtration removes the vast majority of microbial nutrients; the filling process employs high-temperature short-time sterilization and aseptic filling technology to ensure commercial sterility; the packaging container is made of light- and oxygen-blocking materials, and the bottle cap contains an oxygen absorber to further reduce the risk of oxidation; and temperature fluctuations are controlled during product storage to slow down the rate of physicochemical changes.

[0050] The workflow of this invention begins with the preparation of the fermentation substrate: First, glutinous rice is cleaned by a mechanical washing device to remove impurities and then transferred to a soaking tank. A counter-current osmosis soaking technology is used to control the water temperature within the range of 25 to 30 degrees Celsius for 4 to 6 hours, resulting in a glutinous rice moisture content of 30% to 35%. After soaking, the glutinous rice is drained and transported to a continuous cooking equipment, where it is cooked for 25 to 35 minutes under a steam pressure of 0.1 to 0.15 MPa to achieve complete gelatinization, with a gelatinization degree of over 90%. The cooked rice is then mixed with purified water treated by reverse osmosis at a mass ratio of 1:2 to 1:3 in a mixing tank, and a homogeneous suspension is formed by a turbine agitator at a speed of 200 rpm.

[0051] Subsequently, a compound sugar source of granulated sugar and maltose was added. During the addition of the sugar source, the temperature of the mixture was maintained at 40 to 45 degrees Celsius to prevent crystallization. The mass ratio of granulated sugar to maltose was 3:1 to 5:1. The first stage of fermentation was carried out in a temperature-controlled fermentation tank: after three-stage expansion and activation, the rice wine koji was inoculated into the fermentation substrate at an inoculum rate of 0.8% to 1.2%, and uniform distribution was achieved through multi-layer radial flow stirring blades at a speed of 50 rpm. Fermentation was carried out in a sealed environment at 25 to 30 degrees Celsius for 3 to 5 days. During this period, the temperature fluctuation was maintained within ±0.5 degrees Celsius through a coil heat exchange system, and the pH value was monitored online and kept within the range of 3.8 to 4.2.

[0052] The second stage of fermentation begins with solid-liquid separation: the primary fermentation mash is filtered through a plate and frame filter press at an operating pressure of 0.4 to 0.6 MPa, and a clear liquid is obtained using a filter cloth with a specific pore size; after the clear liquid is transferred to the secondary fermentation tank, 5% to 8% sucrose syrup is added, and activated wine yeast is inoculated at a rate of 0.5 to 1.5 grams per liter;

[0053] The fermentation process is carried out in a closed environment at 18 to 22 degrees Celsius for 5 to 7 days, with the temperature reduced by 1 to 2 degrees Celsius each day through a step-down cooling control strategy.

[0054] Termination and filling stage: The secondary fermentation broth is cooled to below 4 degrees Celsius through a three-stage plate heat exchanger, first pre-cooled to 15 degrees Celsius with chilled water, then cooled to 8 degrees Celsius with ethylene glycol solution, and finally lowered to the target temperature by liquid nitrogen injection.

[0055] The cooled fermentation broth is filtered through a 0.45-micron pore size membrane for sterilization, and then enters a carbonation tower where it is mixed with food-grade carbon dioxide at a pressure of 0.2 to 0.3 MPa.

[0056] The final product is filled in a Class 100 clean environment through an aseptic filling line, with the filling temperature controlled at 4 to 6 degrees Celsius and the carbon dioxide pressure inside the bottle maintained at 0.15 to 0.25 MPa.

[0057] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0058] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0059] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 fermentation process for rice wine soda, characterized in that, The process includes the following steps: S1. Prepare fermentation substrate: Soak and steam glutinous rice to obtain cooked rice material. Mix cooked rice material with purified water and add sugar source to form initial fermentation substrate. Sugar source includes white sugar and maltose, and the mass ratio of white sugar to maltose is 3:1 to 5:

1. S2. Carry out the first stage of fermentation. Add rice wine koji to the initial fermentation substrate and stir evenly. Ferment in a closed container at a temperature of 25 degrees Celsius to 30 degrees Celsius for 3 to 5 days to obtain primary rice wine mash. S3. The second stage of fermentation is carried out by pressing and filtering the primary rice wine mash to obtain the clear liquid. Sucrose syrup is added to the clear liquid and wine yeast is inoculated. The amount of sucrose syrup added is 5% to 8% of the mass of the clear liquid, and the amount of wine yeast inoculated is 0.5 to 1.5 grams per liter of clear liquid. The mixture is fermented in a closed system at a temperature of 18 to 22 degrees Celsius for 5 to 7 days to obtain the secondary fermentation liquid. S4. To terminate and fill the fermentation, the secondary fermentation liquid is cooled to below 4 degrees Celsius to terminate the fermentation activity. After being sterilized by membrane filtration, it is introduced into a pressurized container for carbonation treatment and finally bottled to obtain the finished rice wine soda.

2. The fermentation process for rice wine soda as described in claim 1, characterized in that, In the preparation of the fermentation substrate, the glutinous rice is soaked for 4 to 6 hours, the cooking pressure is 0.1 MPa to 0.15 MPa, and the cooking time is 25 to 35 minutes; the mass ratio of the cooked rice to purified water is 1:2 to 1:

3.

3. The fermentation process for rice wine soda as described in claim 1, characterized in that, In the first stage of fermentation, the amount of rice wine koji inoculated is 0.8% to 1.2% of the total mass of the initial fermentation substrate; the relative humidity of the closed fermentation environment is controlled between 75% and 85%.

4. The fermentation process for rice wine soda as described in claim 1, characterized in that, In the second stage of fermentation, the pressure filtration process is carried out using a plate and frame filter press at an operating pressure of 0.4 MPa to 0.6 MPa; the wine yeast strain is activated dry yeast, which is rehydrated for 15 minutes at 35 degrees Celsius with warm water at a weight ratio of 1:10 before use.

5. The fermentation process for rice wine soda as described in claim 1, characterized in that, During the termination and filling process, the membrane filtration sterilization uses a polyethersulfone filter membrane with a pore size of 0.45 micrometers; the carbonation treatment is carried out by introducing carbon dioxide gas into a pressurized container at a temperature of 0 to 4 degrees Celsius to maintain the pressure at 0.2 MPa to 0.3 MPa for 30 minutes.

6. The fermentation process for rice wine soda as described in claim 1, characterized in that, The process also includes adding a flavor modifier to the secondary fermentation broth after the second stage of fermentation is completed and before termination and filling. The flavor modifier comprises citric acid and ascorbic acid, wherein the amount of citric acid added is 0.05% to 0.1% of the mass of the secondary fermentation broth, and the amount of ascorbic acid added is 0.01% to 0.02% of the mass of the secondary fermentation broth.

7. A rice wine soda product prepared by the fermentation process described in any one of claims 1 to 6, characterized in that, The product contains alcohol produced by two-stage fermentation of glutinous rice, carbon dioxide gas introduced by yeast fermentation and carbonation treatment, and unconsumed sugar; wherein the alcohol content is 0.8% to 2.5% by volume, and the carbon dioxide gas pressure is 0.15 MPa to 0.25 MPa at 20 degrees Celsius.

8. The rice wine soda product as described in claim 7, characterized in that, The product also contains citric acid and ascorbic acid from flavor modifiers, with citric acid content ranging from 200 mg / L to 500 mg / L and ascorbic acid content ranging from 50 mg / L to 100 mg / L.

9. A rice wine soda product as described in claim 7, characterized in that, The product has a sugar content ranging from 5 g / L to 15 g / L, and its sugar composition includes residual maltose, sucrose, and glucose and fructose produced during fermentation.

10. A rice wine soda product as described in claim 7, characterized in that, This product, without the addition of any artificial preservatives, has a shelf life of no less than 90 days when stored in sealed packaging at an ambient temperature of 4 to 25 degrees Celsius.

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