A bubble rice wine and its secondary fermentation process

Abstract

The application belongs to the field of food, and particularly relates to a kind of bubble rice wine and its secondary fermentation process. The secondary fermentation process comprises the following steps: after washing glutinous rice, it is soaked and cooked in turn to obtain steamed glutinous rice; after the steamed glutinous rice is spread and cooled, it is added with starter and stirred to obtain mixed starter glutinous rice; the mixed starter glutinous rice is saccharified to obtain saccharified glutinous rice; the saccharified glutinous rice is subjected to first fermentation to obtain first fermentation glutinous rice; the first fermentation glutinous rice is subjected to second fermentation to obtain second fermentation glutinous rice; the second fermentation glutinous rice is isobaric filled, capped and sterilized to obtain the bubble rice wine. The application produces molecular level carbon dioxide through secondary fermentation, and is isobaric canned, so that the obtained bubble rice wine has dense and lasting bubbles, rich flavor and delicate taste, solves the problems of coarse and loose bubbles, easy overflow and uneven distribution in the process of adding carbon dioxide, and realizes stable mass production of bubble rice wine.

Description

Technical Field

[0001] This invention belongs to the food industry, specifically relating to a sparkling rice wine and its secondary fermentation process. Background Technology

[0002] Rice wine, also known as fermented glutinous rice, sweet wine, or laozhao, is a traditional fermented food made primarily from glutinous rice through fermentation with yeast. Rice wine falls somewhere between alcohol and food, possessing both the mellow aroma of wine and the sweetness of rice. Rich in glucose, amino acids, vitamins, and various trace elements, it is a traditional fermented food that combines deliciousness, nutrition, and health benefits, and is widely loved by consumers throughout my country.

[0003] In recent years, with the upgrading of consumption and the rise of young consumers, low-alcohol, slightly tipsy, and refreshing sparkling rice wine has gradually become a market hotspot. Sparkling rice wine adds the refreshing taste of carbonation to traditional rice wine, retaining the aroma and sweetness of rice wine while giving it a pleasant and stimulating sensation similar to champagne and sparkling wine. It is suitable for various consumption scenarios such as dining and gatherings, and market demand continues to grow.

[0004] However, commercially available rice wine currently employs two main production processes: one is plain, non-carbonated rice wine, which has no effervescent taste; the other is a process that involves externally introducing carbon dioxide during the bottling process, where carbon dioxide gas is forced into the rice wine under high pressure and then quickly sealed to retain the gas. The aforementioned external carbon dioxide introduction process has several drawbacks:

[0005] (1) Poor bubble quality: The carbon dioxide introduced from the outside dissolves in the rice wine by physical pressure. The gas molecules are unevenly distributed in the rice wine, and the resulting bubbles are large in size and loosely arranged. When drinking, the taste is rough and not delicate enough. When the bubbles break in the mouth, they produce a harsh cutting sensation and lack the dense and smooth taste experience unique to naturally fermented bubbles.

[0006] (2) Poor gas stability: Since carbon dioxide is dissolved by external pressure rather than produced in situ by the fermentation of rice wine itself, when the temperature of the wine rises or during the time interval between filling and sealing, the dissolved carbon dioxide is very easy to escape from the wine, resulting in loss of carbon dioxide content in the product and uneven content between bottles. The bubbles are not persistent enough during the shelf life and the bubbles dissipate quickly after opening.

[0007] (3) Poor flavor coordination: The external carbon dioxide can only provide a carbonation sensation and cannot form a synergistic effect with the fermentation flavor substances of rice wine. The product has a single flavor, and there is a lack of integration between rice aroma, ester aroma and effervescence. The overall flavor is not rich enough.

[0008] (4) Insufficient gas breakage: The external filling process relies on high pressure to force carbon dioxide into the wine. The gas is not broken up in the wine, resulting in a high proportion of large bubbles, which further aggravates the problems of rough taste and unstable gas.

[0009] Currently, there is no mature, mass-production process on the market for preparing sparkling rice wine by generating carbon dioxide in situ through secondary fermentation within bottles / tanks. While traditional rice wine fermentation also produces carbon dioxide, the fermentation conditions are difficult to control, the gas cannot be effectively retained in the wine, and over-fermentation can lead to problems such as excessively high alcohol content, decreased sugar content, and flavor imbalance. Therefore, developing a rice wine production process that can generate a rich and persistent carbon dioxide in situ through secondary fermentation within bottles / tanks while ensuring a rich and stable flavor has become a pressing technical problem to be solved in this field. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a sparkling rice wine and its secondary fermentation process. This invention generates molecular-level carbon dioxide through secondary fermentation, followed by isobaric bottling, which solves the problems of ordinary sparkling rice wine's own fermentation producing carbon dioxide being difficult to retain effectively, while externally introduced carbon dioxide results in large, loose, unevenly distributed bubbles and a rough taste. This invention achieves mass production of carbon dioxide generated in situ through secondary fermentation in the bottle / can, producing dense and long-lasting bubbles.

[0011] The present invention provides a secondary fermentation process for sparkling rice wine, the secondary fermentation process comprising the following steps: (1) After rinsing the glutinous rice, soak it and steam it to obtain steamed glutinous rice; (2) After the steamed glutinous rice has cooled, add yeast and stir to obtain yeast-mixed glutinous rice; (3) The mixed glutinous rice is saccharified to obtain saccharified glutinous rice; (4) The saccharified glutinous rice is subjected to a first fermentation to obtain primary fermented glutinous rice; (5) The first-fermented glutinous rice is fermented a second time to obtain second-fermented glutinous rice; (6) After the secondary fermented glutinous rice is filled into bottles, sealed and sterilized, the sparkling rice wine is obtained.

[0012] Preferably, in step (1), the glutinous rice is washed and soaked for 4-13 hours, and then steamed at a positive pressure of 1-2 kPa with an air inlet pressure of 25-30 kPa to obtain steamed glutinous rice.

[0013] Preferably, in step (2), the steamed glutinous rice is cooled to 20-36°C, and then Rhizopus mold is added and stirred. The amount of Rhizopus mold added is 0.3-0.5 wt% of the steamed glutinous rice, to obtain mixed glutinous rice.

[0014] Preferably, in step (3), the mixed glutinous rice is saccharified at 25-36℃ for 3-5 days, and the saccharification ends when the sugar content is ≥35Brix, thus obtaining saccharified glutinous rice.

[0015] Preferably, in step (4), the saccharified glutinous rice is diluted with purified water to reduce the sugar content to 12-14 Brix, and then fermented at 19-21℃ for 45-50 hours. The first fermentation ends when the alcohol content reaches 1-3% vol and the sugar content reaches 9-11 Brix, thus obtaining the first fermented glutinous rice.

[0016] Preferably, in step (5), glycogen or fruit juice is added to the primary fermented glutinous rice to increase the sugar content to 12-14 Brix, and then fermented at 3-5℃ for 10-14 hours. When the alcohol content reaches 2-4% vol, the sugar content reaches 10-12 Brix, and the pressure reaches 0.25-0.35 MPa (a large amount of carbon dioxide is generated during the fermentation process), the secondary fermentation ends, and secondary fermented glutinous rice is obtained.

[0017] Preferably, in step (6), the secondary fermented glutinous rice is filled with isobaric filler and sealed, and then sterilized at 84-86℃ for 20-30 minutes to obtain the sparkling rice wine.

[0018] Based on the same technical concept, the present invention provides a sparkling rice wine obtained by the above-mentioned secondary fermentation process, wherein the sparkling rice wine has an alcohol content of 2-4% vol and a sugar content of 10-12 Brix.

[0019] The beneficial effects of this invention are as follows: 1. Dense and persistent bubbles, delicate and smooth taste: This invention generates carbon dioxide in situ through secondary fermentation in the bottle / can. Yeast slowly metabolizes glycogen under low temperature and low pressure conditions. The generated carbon dioxide is uniformly dissolved in the wine at the molecular level, forming small and densely packed bubbles. When drinking, the taste is dense and smooth, without the roughness and harshness unique to external aeration processes. Moreover, the bubbles have good stability in the wine and their persistence after opening is significantly better than that of externally aerated products.

[0020] 2. Rich and complex flavor with harmonious layers: During the saccharification stage, the starch in glutinous rice is fully converted into fermentable sugars such as glucose. During the primary fermentation stage, yeast uses glycogen to generate various flavor substances such as acids, esters, and alcohols. During the secondary fermentation stage, by supplementing glycogen or fruit juice, the synthesis and enrichment of flavor substances are further promoted, so that the flavor substances such as sugars, acids, esters, and alcohols in the rice wine coexist harmoniously. The aroma of rice, esters, and bubbles are integrated into one, and the product has a rich and complex flavor, which is significantly better than products with single exogenous carbonation.

[0021] 3. Stable and uniform carbon dioxide, resulting in good product consistency: The carbon dioxide of this invention is generated in situ during fermentation, forming a stable dissolution balance with the wine, rather than relying on external high pressure physical dissolution; at the same time, the secondary fermentation is carried out in a sealed bottle / tank, and the carbon dioxide produced during fermentation is directly sealed in the container, avoiding gas loss during the filling and capping intervals. The carbon dioxide content is uniform between bottles, and the bubble stability is significantly improved during the shelf life.

[0022] 4. Low-temperature fermentation preserves nutrients and flavor: The secondary fermentation of this invention is carried out at a low temperature of 3-5℃. The low temperature environment inhibits the growth of miscellaneous bacteria and the excessive oxidation of flavor substances, thus preserving the amino acids, vitamins and other nutrients in the rice wine and the fresh rice aroma to the maximum extent. At the same time, the low temperature is conducive to the dissolution and enrichment of carbon dioxide in the wine, further improving the density and persistence of the bubbles.

[0023] 5. Adding glycogen / juice has the dual function of adjusting sugar content and flavoring: Before the secondary fermentation, glycogen or juice is added. On the one hand, the sugar content is adjusted to a range suitable for secondary fermentation, providing a fermentable substrate for yeast. On the other hand, the addition of juice gives rice wine a unique fruity aroma and flavor, enriching the flavor profile of the product. Different juices can be flexibly selected according to market demand to develop a diversified product series. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] This invention provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) After rinsing the glutinous rice, soak it for 4-13 hours. Then, steam the rice at a positive pressure of 1-2 kPa with an air intake pressure of 25-30 kPa to obtain steamed glutinous rice. (2) Spread the steamed glutinous rice to cool to 20-36℃, then add Rhizopus and stir. The amount of Rhizopus added is 0.3-0.5 wt% of the steamed glutinous rice to obtain mixed glutinous rice. (3) At 25-36℃, the mixed glutinous rice is saccharified for 3-5 days. Saccharification ends when the sugar content is ≥35 Brix, and saccharified glutinous rice is obtained. (4) Dilute the saccharified glutinous rice with purified water to reduce the sugar content to 12-14 Brix, and then ferment it at 19-21℃ for 45-50 hours. When the alcohol content reaches 1-3% vol and the sugar content reaches 9-11 Brix, the first fermentation is completed, and the first fermented glutinous rice is obtained. (5) Add glycogen or fruit juice to the primary fermented glutinous rice to increase the sugar content to 12-14 Brix, and then ferment at 3-5℃ for 10-14h. When the alcohol content reaches 2-4%vol, the sugar content reaches 10-12 Brix, and the pressure reaches 0.25-0.35MPa, the secondary fermentation ends, and secondary fermented glutinous rice is obtained. (6) After the secondary fermented glutinous rice is filled with isobaric filling and sealed, it is then sterilized at 84-86℃ for 20-30 minutes to obtain the sparkling rice wine.

[0026] Example 1 This embodiment provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) Soaking and steaming: Wash 100kg of glutinous rice three times with clean water until the wash water is clear. Then soak it in purified water for 8 hours. After soaking, drain the water and spread the glutinous rice into the steaming equipment. The air pressure of the equipment is 25kPa. Maintain a positive pressure of 1kPa for 25 minutes to obtain steamed glutinous rice. In this step, washing can remove dust, impurities and free starch from the surface of glutinous rice, and prevent the rice from becoming sticky and clumpy after steaming. Soaking allows the glutinous rice to fully absorb water and expand, and the starch granules are moderately gelatinized, which is conducive to uniform steaming and saccharification and enzymatic hydrolysis in the later stage. The pressure steaming can fully gelatinize the starch of glutinous rice, and the rice is cooked thoroughly but not mushy, with a consistent softness inside and out, providing a good substrate structure for the growth and reproduction of Rhizopus and saccharification.

[0027] (2) Cooling and adding koji: Take the steamed glutinous rice out of the rice steamer and spread it evenly on a clean cooling platform. Let it cool naturally to 28°C. Then add 0.4% of the weight of the steamed glutinous rice with Rhizopus mold (i.e., 0.4 kg of Rhizopus mold). Mix thoroughly to obtain koji-mixed glutinous rice. In this step, cooling to 28°C is to reduce the temperature of the rice to the suitable growth temperature range of Rhizopus mold, avoiding the high temperature from killing the Rhizopus mold spores. Rhizopus mold plays a saccharification role in rice wine brewing. The amylase it secretes can decompose glutinous rice starch into glucose. The 0.4% inoculation amount can ensure the saccharification speed and fullness, and will not increase the off-flavor due to excessive inoculation amount. Thorough mixing ensures that the Rhizopus mold spores are in uniform contact with each grain of rice, so that the saccharification process is carried out synchronously and evenly.

[0028] (3) Saccharification: The mixed glutinous rice is transferred to a saccharification tank and saccharified at 30°C for 4 days, with stirring once a day during the period. At the end of saccharification, the sugar content is measured to reach 36 Brix, and saccharified glutinous rice is obtained. In this step, 30°C is the suitable temperature for the growth, reproduction and enzyme production of Rhizopus. At this temperature, Rhizopus is vigorous and the saccharification efficiency is high. After 4 days of saccharification, the starch in the glutinous rice is fully converted into fermentable sugars such as glucose, and the sugar content reaches 36 Brix, providing sufficient carbon source for the subsequent primary fermentation. At the same time, the metabolism of Rhizopus during saccharification will also produce a small amount of organic acids and flavor precursors, laying the foundation for the flavor of rice wine. Stirring every day can release the heat generated by saccharification, prevent the local temperature from being too high, and allow the material to fully contact with oxygen, promoting the growth of Rhizopus.

[0029] (4) Primary fermentation: Add purified water to the saccharified glutinous rice to dilute the sugar content to 13 Brix, then quickly cool it to 20°C and transfer it to a fermentation tank to ferment at 20°C for 48 hours. At the end of fermentation, the alcohol content is measured to be 2% vol and the sugar content to be 10 Brix, thus obtaining primary fermented glutinous rice. In this step, adding purified water to dilute the sugar content from 36 Brix to 13 Brix serves two purposes: firstly, it adjusts the sugar concentration to the appropriate osmotic pressure range for yeast, avoiding high sugar levels that inhibit yeast activity; secondly, it provides sufficient water and fermentable sugars for the yeast. Quickly cooling to 20°C inhibits further saccharification by Rhizopus and activates the yeast to enter the alcoholic fermentation stage. During 48 hours of fermentation at 20°C, the yeast uses glucose for alcoholic fermentation, producing alcohol and carbon dioxide, as well as flavor compounds such as acids, esters, and alcohols. The completion of primary fermentation is indicated by an alcohol content of 2% vol and a sugar content of 10 Brix. At this point, the wine retains an appropriate amount of residual sugar and active yeast, preparing it for secondary fermentation.

[0030] (5) Secondary fermentation: Add glycogen to the primary fermented glutinous rice to adjust the sugar content to 13 Brix. After thorough mixing, quickly cool to 4°C and transfer to a pressure fermentation tank. Ferment at 4°C for 12 hours. At the end of fermentation, the alcohol content is measured to be 3% vol, the sugar content to be 11 Brix, and the pressure inside the tank to be 0.3 MPa, thus obtaining secondary fermented glutinous rice. In this step, adding glycogen increases the sugar content from 10 Brix to 13 Brix, providing a new fermentable substrate for secondary fermentation and restarting the fermentation metabolism of yeast. Quickly cooling to 4°C puts the yeast into a low-temperature, slow fermentation state. At low temperatures, the metabolic rate of yeast decreases, the fermentation process is mild and controllable, and the carbon dioxide produced slowly dissolves into the wine at the molecular level, resulting in denser and finer bubbles. During fermentation, a large amount of carbon dioxide is produced inside the tank, bringing the pressure inside the tank to 0.3 MPa. The high pressure can further increase the solubility of carbon dioxide in the wine, preventing the escape of carbon dioxide produced during fermentation. At the same time, the pressure environment inhibits the growth of miscellaneous bacteria. After 12 hours of fermentation, the alcohol content rose to 3% vol and the sugar content dropped to 11 Brix. The secondary fermentation was carried out appropriately, which produced enough carbon dioxide while retaining the appropriate sweetness and flavor.

[0031] (6) Filling and Sterilization: The secondary fermented glutinous rice is filled into glass bottles using an isobaric filling machine, with a net filling content of 330 mL. The bottles are immediately capped after filling and then sterilized at 85°C for 25 min. After sterilization, the bottles are cooled to room temperature to obtain the sparkling rice wine. In this step, isobaric filling can prevent carbon dioxide from escaping from the wine during the filling process, ensuring a stable gas content in the product; immediately capping after filling can minimize carbon dioxide loss. Sterilization at 85°C for 25 min can kill yeast and other bacteria in the wine, terminate the fermentation process, and prevent continued fermentation in the bottle from causing bottle explosion or flavor deterioration. At the same time, this temperature condition is relatively mild and has less damage to the flavor substances and nutrients of the rice wine, which is conducive to preserving the rich flavor and dense bubbles of the product.

[0032] Example 2 This embodiment provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) Wash 100kg of glutinous rice with clean water, soak it in purified water for 4 hours, drain the water, spread the glutinous rice into the steaming equipment, the air pressure of the equipment is 30kPa, and steam it for 30 minutes with a positive pressure of 2kPa to obtain steamed glutinous rice. (2) Spread the steamed glutinous rice out to cool to 20°C, add 0.3% of the mass of the steamed glutinous rice with Rhizopus mold (i.e., 0.3 kg), mix thoroughly to obtain mixed glutinous rice; (3) Transfer the mixed glutinous rice into a saccharification tank and let it stand at 25°C for 3 days for saccharification. Stir once a day. When the saccharification is finished, the sugar content is 35 Brix, and saccharified glutinous rice is obtained. (4) Add purified water to the saccharified glutinous rice to dilute it to a sugar content of 12 Brix, quickly cool it down to 19°C, and ferment it at 19°C for 45 hours. At the end, the alcohol content is 1% vol and the sugar content is 9 Brix, thus obtaining the first fermented glutinous rice. (5) Add glucose to the primary fermented glutinous rice to adjust the sugar content to 12 Brix, mix well and cool to 3°C, ferment at 3°C ​​for 10 hours. At the end, the alcohol content is 2% vol, the sugar content is 10 Brix and the pressure inside the tank is 0.25 MPa, thus obtaining secondary fermented glutinous rice. (6) The secondary fermented glutinous rice is filled into glass bottles with a net content of 330 mL, sealed immediately, sterilized at 84°C for 20 min, and cooled to obtain the sparkling rice wine.

[0033] Example 3 This embodiment provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) Wash 100kg of glutinous rice with clean water, soak it in purified water for 13 hours, drain the water, spread the glutinous rice into the steaming equipment, the air pressure of the equipment is 26kPa, and steam it for 20 minutes with a positive pressure of 1.2kPa to obtain steamed glutinous rice; (2) Spread the steamed glutinous rice out to cool to 36°C, add 0.5% of the mass of the steamed glutinous rice with Rhizopus mold (i.e., 0.5 kg), mix thoroughly to obtain mixed glutinous rice; (3) Transfer the mixed glutinous rice into a saccharification tank and let it stand at 36°C for 5 days for saccharification. Stir once a day. When the saccharification is finished, the sugar content is 38 Brix, and saccharified glutinous rice is obtained. (4) Add purified water to the saccharified glutinous rice to dilute it to a sugar content of 14 Brix, quickly cool it down to 21°C, and ferment it at 21°C for 50 hours. At the end, the alcohol content is 3% vol and the sugar content is 11 Brix, thus obtaining the first-fermented glutinous rice. (5) Add glucose to the primary fermented glutinous rice to adjust the sugar content to 14 Brix, mix well and cool to 5°C, ferment at 5°C for 14 hours. At the end, the alcohol content is 4% vol, the sugar content is 12 Brix and the pressure inside the tank is 0.35 MPa, thus obtaining secondary fermented glutinous rice. (6) The secondary fermented glutinous rice is filled into glass bottles with a net content of 330 mL, sealed immediately, sterilized at 86°C for 30 min, and cooled to obtain the sparkling rice wine.

[0034] Example 4 This embodiment provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) Wash 100kg of glutinous rice with clean water, soak it in purified water for 10 hours, drain the water, spread the glutinous rice into the steaming equipment, the air pressure of the equipment is 28kPa, and steam it for 22 minutes with a positive pressure of 1.5kPa to obtain steamed glutinous rice. (2) Spread the steamed glutinous rice out to cool to 30°C, add 0.45% of the weight of the steamed glutinous rice with Rhizopus mold (i.e. 0.45 kg), mix thoroughly to obtain mixed glutinous rice; (3) Transfer the mixed glutinous rice into a saccharification tank and let it stand at 32°C for 4 days, stirring once a day. When the saccharification is finished, the sugar content is 37 Brix, and saccharified glutinous rice is obtained. (4) Add purified water to the saccharified glutinous rice to dilute it to a sugar content of 13 Brix, quickly cool it down to 20°C, and ferment it at 20°C for 47 hours. At the end, the alcohol content is 2% vol and the sugar content is 10 Brix, thus obtaining the first fermented glutinous rice. (5) Add a mixture of white peach and passion fruit juice (mass ratio 1:1) to the primary fermented glutinous rice, adjust the sugar content to 13 Brix, mix well and then quickly cool down to 4°C, ferment at 4°C for 12 hours. At the end, the alcohol content is 3% vol, the sugar content is 11 Brix and the pressure inside the tank is 0.3 MPa, thus obtaining secondary fermented glutinous rice. (6) The secondary fermented glutinous rice is filled into glass bottles with a net content of 330 mL, and the bottles are immediately sealed. The bottles are then sterilized at 85°C for 25 min and cooled to obtain the sparkling rice wine.

[0035] Example 5 This embodiment provides a secondary fermentation process for sparkling rice wine, which includes the following steps: (1) Wash 100kg of glutinous rice with clean water, soak it in purified water for 6 hours, drain the water, spread the glutinous rice into the steaming equipment, the air pressure of the equipment is 25kPa, and steam it for 28 minutes under 2kPa positive pressure to obtain steamed glutinous rice. (2) Spread the steamed glutinous rice out to cool to 25°C, add 0.35% of the weight of the steamed glutinous rice with Rhizopus mold (i.e., 0.35 kg), mix thoroughly to obtain mixed glutinous rice; (3) Transfer the mixed glutinous rice into a saccharification tank and let it stand at 28°C for 3 days for saccharification. Stir once a day. When the saccharification is finished, the sugar content is 35 Brix, and saccharified glutinous rice is obtained. (4) Add purified water to the saccharified glutinous rice to dilute it to a sugar content of 12 Brix, quickly cool it down to 19°C, and ferment it at 19°C for 46 hours. At the end, the alcohol content is 1.5% vol and the sugar content is 9.5 Brix, thus obtaining the first-fermented glutinous rice. (5) Add concentrated grape juice to the primary fermented glutinous rice, adjust the sugar content to 12 Brix, mix well and then quickly cool down to 3.5℃, ferment at 3.5℃ for 11 hours. At the end, the alcohol content is 2.5% vol, the sugar content is 10.5 Brix and the pressure inside the tank is 0.28 MPa, thus obtaining secondary fermented glutinous rice. (6) The secondary fermented glutinous rice is filled into aluminum cans with a net content of 330 mL, and the cans are sealed immediately. The cans are sterilized at 84.5℃ for 22 min and cooled to obtain the sparkling rice wine.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A secondary fermentation process for sparkling rice wine, characterized in that, The secondary fermentation process includes the following steps: (1) After rinsing the glutinous rice, soak it and steam it to obtain steamed glutinous rice; (2) After the steamed glutinous rice has cooled, add yeast and stir to obtain yeast-mixed glutinous rice; (3) The mixed glutinous rice is saccharified to obtain saccharified glutinous rice; (4) The saccharified glutinous rice is subjected to a first fermentation to obtain primary fermented glutinous rice; (5) The first-fermented glutinous rice is fermented a second time to obtain second-fermented glutinous rice; (6) After the secondary fermented glutinous rice is filled into bottles, sealed and sterilized, the sparkling rice wine is obtained.

2. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (1), after rinsing the glutinous rice, soak it for 4-13 hours, and then steam it with an air inlet pressure of 25-30 kPa and a positive pressure of 1-2 kPa to obtain steamed glutinous rice.

3. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (2), the steamed glutinous rice is cooled to 20-36℃, and then Rhizopus mold is added and stirred. The amount of Rhizopus mold added is 0.3-0.5wt% of the steamed glutinous rice to obtain mixed glutinous rice.

4. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (3), the mixed glutinous rice is saccharified at 25-36℃ for 3-5 days. Saccharification ends when the sugar content is ≥35Brix, and saccharified glutinous rice is obtained.

5. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (4), the saccharified glutinous rice is diluted with purified water to reduce the sugar content to 12-14 Brix, and then fermented at 19-21℃ for 45-50 hours. The first fermentation ends when the alcohol content reaches 1-3% vol and the sugar content reaches 9-11 Brix, thus obtaining the first fermented glutinous rice.

6. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (5), glycogen or fruit juice is added to the primary fermented glutinous rice to increase the sugar content to 12-14 Brix, and then fermented at 3-5℃ for 10-14 hours. When the alcohol content reaches 2-4% vol, the sugar content reaches 10-12 Brix, and the pressure reaches 0.25-0.35 MPa, the secondary fermentation ends, and secondary fermented glutinous rice is obtained.

7. The secondary fermentation process for sparkling rice wine according to claim 1, characterized in that, In step (6), the secondary fermented glutinous rice is filled with isobaric filler and sealed, and then sterilized at 84-86℃ for 20-30 minutes to obtain the sparkling rice wine.

8. The sparkling rice wine obtained by the secondary fermentation process according to any one of claims 1-7, characterized in that, The sparkling rice wine has an alcohol content of 2-4% vol and a sugar content of 10-12 Brix.