Secondary fermentation process for yellow wine

Abstract

The invention discloses a secondary fermentation process of yellow wine. The secondary fermentation process comprises the following steps: S1, screening yeast: (1) filtering grape juice from grapes, and fermenting to obtain various yeasts; (2) culturing various yeasts in a culture medium; (3) blending finished yellow wine and water to obtain raw wine; (4) extracting a plurality of yeasts, and respectively putting the yeasts into the raw wine for fermentation test; (5) detecting the purine content of the raw wine after fermentation under the action of different yeasts; and S2, secondary fermentation: fermenting the raw wine blended in the step S1 by using the yeast with relatively low purine content after fermentation obtained in the step S1 (4). In the step 1, the alcoholic strength of the raw wine obtained by blending is 5% vol-6% vol, and the glucose content is 16 g / L-19 g / L. The invention provides a secondary fermentation process for yellow rice wine. Purine in the yellow rice wine is reduced through secondary fermentation.

Description

Technical Field

[0001] The present invention relates to the technical field of rice wine fermentation, and more particularly to a secondary fermentation process of rice wine. Background Art

[0002] Huangjiu (yellow rice wine) is made from fermented koji (dice yeast), a fermented product that inherently contains high levels of purines. Huangjiu is primarily brewed from grains such as rice, millet, foxtail millet, and glutinous rice. While these grains themselves have relatively low purine content, a certain amount is produced during the brewing process due to the action of microorganisms and fermentation conditions. The sugars in the raw materials ferment under the action of yeast to produce alcohol and carbon dioxide, which also produces several metabolites, including purines. These purines dissolve in the yellow rice wine, resulting in a relatively high purine content. Reducing the purine content in yellow rice wine is a current challenge. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a secondary fermentation process for yellow rice wine, which reduces purine in yellow rice wine through secondary fermentation.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: a secondary fermentation process of yellow rice wine, comprising the following steps:

[0005] S1: Screening yeast

[0006] ① Filter grape juice from grapes and ferment it to obtain various yeasts;

[0007] ② Cultivate multiple yeasts in culture medium;

[0008] ③ Use finished rice wine and water to mix to obtain raw wine;

[0009] ④ Extract various yeasts and add them into the original wine for fermentation test;

[0010] ⑤ Detect the purine content of the original liquor after fermentation with different yeast species;

[0011] S2: Secondary fermentation

[0012] The yeast with low purine content after fermentation obtained in step S1 ④ is used to ferment the base liquor prepared in step S1 ③.

[0013] In step S1 ③, the alcohol content of the blended base liquor is 5% vol-6% vol, and the glucose content is 16 g / L-19 g / L.

[0014] It is further configured that the fermentation test temperature in step S1 ④ is 15°C-30°C.

[0015] The further setting is that in S2, during fermentation, the yeast inoculation concentration is 4×105 / mL-4×10 7 pieces / mL.

[0016] It is further configured that the fermentation temperature in S2 is controlled at 15°C-30°C.

[0017] A further configuration is that pressure fermentation is adopted in S2.

[0018] It is further configured that, in step ② of S1, the culture medium is prepared as follows:

[0019] ① Prepare TTC lower layer medium: Dissolve 4g-5.05g glucose, 0.8g-1.2g peptone, 0.65-0.8g yeast extract, 0.4g-0.55g potassium dihydrogen phosphate, 0.15g-0.25g magnesium sulfate, 0.1g-0.15g citric acid, and 8g-12g agar in 500mL of distilled water. Sterilize with high pressure steam and pour onto plates to obtain TTC lower layer medium. Confirm sterility by blank culture at 25°C-28°C.

[0020] ② Dilute the fermented grape juice with sterile water to culture yeast;

[0021] ③ Prepare TTC top culture medium: Weigh 2.5g-3.5g glucose and 2g-3g agar and dissolve them in 100ml water. Heat to dissolve and sterilize with high-pressure steam. Aseptically add 0.025g-0.03g TTC bottom culture medium in a water bath at 45℃-50℃. After dissolution, pour the culture medium into a plate and incubate at 25℃-30℃ in the dark. Then, inoculate the TTC top culture medium into 12°BX malt wort using an inoculation loop and incubate at a constant temperature of 25℃-30℃ for 18-25 hours.

[0022] It is further configured that, in step ② of preparing the culture medium, the method for diluting the cultured yeast is:

[0023] Take 1 dose of fermented grape juice and put it into a test tube with 9 doses of sterile water and shake it well, which is 10. -1 Tube;

[0024] From 10 -1 One dose is drawn from the tube and placed in 9 doses of sterile water test tubes, which is counted as 10 -2 Tube;

[0025] Prepare 10 in the same way -3 Tube, 10 -4 Tube, 10 -5 Tube, 10 -6 Tube, 10 -7 Tube, 10 -8 Tube;

[0026] The diluted bacterial solution in the test tube was inoculated into sterile culture dishes containing TTC lower culture medium that had been blank cultured, spread evenly, and cultured in a biochemical incubator at 25℃-30℃ for 2-3 days.

[0027] A further setting is that 1 dose is 1 ml.

[0028] In summary, the present invention has the following beneficial effects:

[0029] Multiple strains are cultivated by fermenting grape juice, and suitable fermentation strains are screened out through fermentation experiments for secondary fermentation of rice wine, which is beneficial to reducing the purine content in the rice wine after the secondary fermentation. At the same time, the temperature, yeast inoculation concentration, pressure and initial sugar content during the secondary fermentation process are controlled to further reduce the purine content in the rice wine. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart of Example 1;

[0031] Figure 2 is a cross-sectional schematic diagram of embodiment 2;

[0032] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0033] Figure 4 for Figure 2 Enlarged view of point B in the middle;

[0034] Figure 5 for Figure 2 Schematic cross-sectional view in the MM direction.

[0035] Figure numerals: fermentation tank 1, cavity 11, side wall 12, turntable 1, convex body 21, turn plate 2, insert tube 1, 31, connecting sleeve 32, insert tube 2, 33, connecting pipe 34, combined pipe 4, tube body 1, 41, tube body 2, 42, tube body 3, 43, turn plate 3, 5, pipeline assembly 6, fixing seat 1, 7, disk 1, 71, cavity 1, 711, inner wall surface 712, buoyancy ball 713, rotary joint 1, 72, cover plate 73, interface 731, fixing seat 2, 8, disk 2, 81, cavity 2, 811, rotary joint 2, 82. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] like Figure 1As shown, a secondary fermentation process of yellow rice wine comprises the following steps:

[0038] S1: Screening yeast

[0039] ① Crush the grapes, filter out the grape juice, and put it into a sterile conical flask for fermentation for 4 days to obtain various yeasts.

[0040] ② Cultivate various yeasts in a culture medium. The culture medium is prepared as follows:

[0041] First, prepare TTC lower layer medium: dissolve 4g-5.05g of glucose, 0.8g-1.2g of peptone, 0.65-0.8g of yeast extract, 0.4g-0.55g of potassium dihydrogen phosphate, 0.15g-0.25g of magnesium sulfate, 0.1g-0.15g of citric acid, and 8g-12g of agar in 500 mL of distilled water. After high-pressure steam sterilization, pour the medium onto a plate to obtain TTC lower layer medium. Perform blank culture at 25℃-28℃ to confirm sterility.

[0042] Secondly, the fermented grape juice is diluted with sterile water to culture yeast.

[0043] Finally, prepare the TTC upper culture medium: weigh 2.5g-3.5g glucose and 2g-3g agar, dissolve them in 100ml water, heat to dissolve, sterilize with high-pressure steam, and aseptically add 0.025g-0.03g TTC lower culture medium TTC in a water bath at 45℃-50℃. After dissolution, pour it into a plate and culture in the dark at 25℃-30℃. Then, use an inoculation loop to inoculate the TTC upper culture medium into 12°BX malt juice and culture at a constant temperature of 25℃-30℃ for 18 hours to 25 hours.

[0044] ③ Blending base wine: Blend finished rice wine and water to obtain base wine. The blended base wine has an alcohol content of 5% vol-6% vol and a glucose content of 16g / L-19g / L.

[0045] ④ Extract various yeasts and put them into the original wine for fermentation test; the fermentation test temperature is 15℃-30℃, and the yeast inoculation concentration is 4×10 5 / mL-4×10 7 / mL, the alcohol content of the original wine is 5%vol-6%vol, and the glucose content is 16g / L-19g / L.

[0046] ⑤ Take samples to test the purine content, and test the purine content of the original liquor after fermentation with different types of yeast.

[0047] S2: Secondary fermentation

[0048] The yeast with low purine content after fermentation obtained in step ② of S1 (i.e., yeast of category 5 in Table 1) is used to ferment the base liquor.

[0049] Example 1:

[0050] S1: Screening yeast

[0051] ① Crush the grapes, filter out the grape juice, and put it into a sterile conical flask for fermentation for 4 days to obtain various yeasts.

[0052] ② Cultivate the various yeasts in a culture medium. The culture medium is prepared as follows:

[0053] Prepare TTC lower layer medium: dissolve 5.05 g glucose, 1.0 g peptone, 0.75 g yeast extract, 0.5 g potassium dihydrogen phosphate, 0.2 g magnesium sulfate, 0.135 g citric acid, and 10 g agar in 500 mL of distilled water. Sterilize with high-pressure steam and pour onto plates to obtain TTC lower layer medium. Perform a blank culture at 28°C to confirm sterility.

[0054] The fermented grape juice is diluted with sterile water to culture yeast. Specifically, 1 ml of fermented grape juice is placed in a test tube with 9 ml of sterile water, shaken, and counted as 10 -1 Same as above method, from 10 -1 1 ml is drawn from the tube and placed in a 9 ml sterile water test tube, which is counted as 10 -2 Similarly, prepare 10 -3 Tube, 10 -4 Tube, 10 -5 Tube, 10 -6 Tube, 10 -7 Tube, 10 -8 The diluted bacterial solution in the test tube was inoculated into sterile culture dishes containing blank cultured TTC lower layer medium, spread evenly, and cultured in a biochemical incubator at 28°C for 3 days, checking the growth of the colonies every day.

[0055] Prepare TTC top layer medium: Weigh 3g glucose and 2g agar and dissolve in 100ml water. Heat to dissolve, then autoclave. Aseptically add 0.03g TTC bottom layer medium in a water bath at approximately 50°C, dissolve, and pour onto plates. Incubate at 28°C in the dark. Select red colonies with uniform morphology, size, and plump colonies based on their growth. Observe the colonies and examine their cell morphology microscopically to confirm that all selected strains are yeasts. Inoculate the strains with an inoculating loop into 12°BX malt wort and incubate at 28°C for 20 hours.

[0056] Five different types of yeast were obtained by culture.

[0057] ③ Blending of raw wine: Use finished rice wine such as Jiafan wine and Xiangxue wine to mix with water to obtain raw wine.

[0058] The alcohol content of the blended base liquor is 5.35% vol and the glucose content is 17.2 g / L.

[0059] ④ Extract the five yeasts obtained in step ② and place them in the original liquor for fermentation test. The specific test method is to fill 700mL of original liquor into each glass bottle and sterilize it in a water bath. After cooling, inoculate a loopful of yeast and ferment in a 30℃ incubator until glucose fermentation is basically complete. Among them, the other fermentation conditions are: the yeast inoculation concentration is 4×10 6 / mL, the actual initial alcohol content of the original wine is 5.35%vol, and the initial sugar content is 17.2g / L.

[0060] ⑤ Detect the purine content of the original liquor after fermentation with 5 different types of yeast.

[0061] For the five yeast types obtained in sampling step ② in Table 1, purine analysis data was recorded after fermentation of base liquor with the corresponding yeasts. Type 5 yeast produced the lowest purine content after fermentation of base liquor. Type 5 yeast is the optimal target yeast and is most suitable for secondary fermentation of base liquor aimed at reducing purine levels.

[0062] Table 1

[0063] Yeast No. Total purine before fermentation (mg / L) Total purine after fermentation (mg / L) 1 5.98 7.51 2 5.98 4.19 3 5.98 8.65 4 5.98 3.77 5 5.98 2.92

[0064] In order to further analyze the effect of fermentation conditions on the purine content of secondary fermentation, it is necessary to conduct experimental analysis on the conditions of secondary fermentation to optimize the fermentation conditions, including temperature optimization, yeast inoculation concentration optimization, whether to ferment under pressure and initial sugar content optimization.

[0065] Temperature Optimization Test: Fermentation was performed at different temperatures, maintaining consistent yeast inoculum concentration, starting alcohol content, starting alcohol content, and starting sugar content. See Table 2 for details. Table 2 shows that fermentation at lower temperatures can reduce total purine levels. However, lower temperatures can slow fermentation and increase the risk of contamination. Therefore, a fermentation temperature of 20°C was selected as the optimal temperature in this example.

[0066] Table 2

[0067] Test number Yeast inoculum concentration (cells / mL) Fermentation temperature (℃) Initial alcohol content (%vol) Initial sugar content (g / L) Initial purine (mg / L) Total purine after secondary fermentation (mg / L) Fermentation time (days) 1 <![CDATA[4×10 6 ]]> 15 5.35 17.2 5.98 1.97 7 2 <![CDATA[4×10 6 ]]> 20 5.35 17.2 5.98 2.13 4 3 <![CDATA[4×10 6 ]]> 25 5.35 17.2 5.98 2.60 2 4 <![CDATA[4×10 6 ]]> 30 5.35 17.2 5.98 2.92 1

[0068] Yeast inoculum concentration optimization: At 20°C, different yeast inoculum concentrations were selected. While other conditions remained unchanged, the effects of different inoculum concentrations on purine production were analyzed. See Table 3 below for details.

[0069] Table 3

[0070] Test number Yeast inoculum concentration (cells / mL) Fermentation temperature (℃) Initial alcohol content (%vol) Initial sugar content (g / L) Initial purine (mg / L) Total purine after secondary fermentation (mg / L) Fermentation time 1 <![CDATA[4×10 5 ]]> 20 5.35 17.2 5.98 2.06 6 2 <![CDATA[4×10 6 ]]> 20 5.35 17.2 5.98 2.13 4 3 <![CDATA[4×10 7 ]]> 20 5.35 17.2 5.98 2.87 2

[0071] According to the test results in Table 3, it is known that different inoculation concentrations have a greater impact on the fermentation time. Too large an inoculation amount can easily lead to an increase in purine content. Therefore, as the optimal choice, the inoculation concentration selected in this example is 4×10 6 pieces / mL.

[0072] Whether to optimize fermentation under pressure: see Table 4 below for details.

[0073] Table 4

[0074] Test number Whether to ferment under pressure Yeast inoculum concentration (cells / mL) Fermentation temperature (℃) Initial alcohol content (%vol) Initial sugar content (g / L) Initial purine (mg / L) Total purine after secondary fermentation (mg / L) 1 yes <![CDATA[4×10 6 ]]> 20 5.35 17.2 5.98 1.71 2 no <![CDATA[4×10 6 ]]> 20 5.35 17.2 5.98 2.13

[0075] According to the test in Table 4, fermentation under pressure can further reduce the purine content after fermentation. Therefore, as the best choice, this embodiment selects fermentation under pressure.

[0076] For details on the selection of starting sugar content, see Table 5.

[0077] Table 5

[0078] Test number Whether to ferment under pressure Yeast inoculum concentration (cells / mL) Fermentation temperature (℃) Initial alcohol content (%vol) Initial sugar content (g / L) Initial purine (mg / L) Total purine after secondary fermentation (mg / L) 1 yes <![CDATA[4×10 6 ]]> 20 5.35 17.2 5.98 1.71 2 yes <![CDATA[4×10 6 ]]> 20 5.78 23.6 7.85 3.55 3 yes <![CDATA[4×10 6 ]]> 20 5.89 32.5 6.47 4.64

[0079] According to the test in Table 5, a high initial sugar content may easily lead to yeast autolysis, which is not conducive to reducing the purine content. Therefore, as the optimal choice, the glucose content in this example is selected to be 17 g / L.

[0080] Example 2:

[0081] The fermentation temperature is regulated by controlling the room temperature of the fermentation chamber. Since the fermentation process produces a temperature rise phenomenon, and the closer to the center of the fermentation barrel, the less likely the heat is to dissipate, the local temperature in the fermentation barrel is higher than the set temperature, which directly affects the purine value after the secondary fermentation. In order to solve the defects of the traditional fermentation equipment (the traditional fermentation equipment is used for fermentation in Example 1) on the secondary fermentation process, the rice wine fermentation equipment is improved to improve the fermentation process's ability to control the fermentation temperature.

[0082] like Figure 2 As shown, the improved fermentation equipment includes a fermentation tank 1, which has a cavity 11 within it. The fermentation tank 1 is filled with raw liquor for fermentation. The fermentation tank 1 includes left and right sidewalls 12, each of which is fitted with a turntable 2. The sidewalls 12 are connected to the corresponding turntable 2 via bearings (food-grade bearings), allowing the turntable 2 to rotate along its axis.

[0083] like Figure 2As shown, turntable 1 2 is provided with protrusions 21, which are arranged opposite each other. The left protrusion 21 is mounted with turn plate 2 3, and the right protrusion 21 is mounted with turn plate 3 5. The protrusions 21 are inserted into the corresponding turn plates 2 3 and 3 5. The protrusions 21 are connected to the corresponding turn plates 2 3 and 3 5 via bearings. Both turn plates 2 3 and 3 5 can rotate along their own axes.

[0084] Combine Figure 2 、 Figure 5 A combined pipe 4 is installed between rotating plate 2 3 and rotating plate 3 5 . Two combined pipes 4 are provided, comprising pipe body 1 41 and pipe bodies 2 42 and 3 43 located on the left and right sides of pipe body 1 41 . Pipe bodies 1 41 , 2 42 , and 3 43 are interconnected. One end of pipe body 2 42 is sealed and inserted into rotating plate 2 3 , while the other end is sealed and inserted into pipe body 1 41 . One end of pipe body 3 43 is sealed and inserted into rotating plate 3 5 , while the other end is sealed and inserted into pipe body 1 41 . Cooling water is introduced into combined pipe 4 to reduce the heat generated during the fermentation of the raw liquor in cavity 11 , thereby achieving temperature control. The cooling water temperature is controlled at 19°C-20°C.

[0085] The pump room that controls the water flow is set outside the fermentation chamber, which makes the fermentation environment quieter and provides a better production environment.

[0086] Tube 2 42 is the water inlet, and tube 3 43 is the water outlet. Rotating plate 2 3 is disc-shaped, with tubes 1 41, 2 42, and 3 43 projected onto the disc surface of rotating plate 2 3. The distance from tube 2 42 to the center of rotating plate 2 3 is smaller than the distance from tube 3 43 to the center of rotating plate 2 3. Tube 1 41 is also arc-shaped and concave. The impact of water on the wall of tube 1 41 creates a force that causes tube 1 41 to rotate about the axis of convex body 21. This creates agitation within cavity 11, along with tubes 1 41, 2 42, and 3 43, for uniform temperature control.

[0087] like Figure 2 、 Figure 3 As shown, the rotating plate 2 3 is installed with an insert sleeve 1 31, which is connected to the tube body 2 42, and the rotating disk 1 2 is inserted with an insert sleeve 2 33, the left end of the insert sleeve 2 33 is connected to the connecting pipe 34, the right end of the insert sleeve 2 33 is connected to the connecting sleeve 32, and the left end of the connecting sleeve 32 is threadedly connected and inserted into the insert sleeve 2 33.

[0088] like Figure 2 、 Figure 4As shown, the fermentation equipment also includes a fixed seat 7, the inner wall of which is connected to a disk 71 via a bearing. The disk 71 is provided with a cavity 711. A cover plate 73 is installed on the left side of the disk 71. The cover plate 73 is provided with an interface 731. The left side of the interface 731 is connected to a rotary joint 72. The rotary joint 72 is externally connected to the water inlet pipe and is coaxially arranged with the disk 71. The cavity 711 is connected to the pipe 34 and the rotary joint 72. Similarly, Figure 2 As shown, the fermentation equipment also includes a second fixing base 8, which is rotatably connected to a second disk body 81. The second disk body 81 has a second cavity 811 disposed therein. The second disk body 81 is equipped with a second rotary joint 82, which is connected to the second cavity 811. The third rotating plate 5 is equipped with a pipe assembly 6, one end of which is connected to the second cavity 811 and the other end is connected to the third pipe body 43.

[0089] like Figure 2 、 Figure 4 As shown, the disk 1 71 includes an inner wall surface 712, and the connection port between the disk 1 71 and the connecting pipe 34 is located radially inward of the inner wall surface 712. A buoyancy ball 713 is suspended from the inner wall surface 712 by a suspension rope. When the buoyancy ball 713 is located at an upper position, the floating direction of the buoyancy ball 713 is away from the connection port between the disk 1 71 and the connecting pipe 34, and the buoyancy ball 713 does not cause blockage to the connection port between the disk 1 71 and the connecting pipe 34; when the buoyancy ball 713 is located at a lower position, the floating direction of the buoyancy ball 713 is close to the connection port between the disk 1 71 and the connecting pipe 34. As water flows into the connecting pipe 34, the buoyancy ball 713 is easily moved close to the connection port between the disk 1 71 and the connecting pipe 34 under the action of the fluid and causes blockage. The occurrence of this blockage phenomenon leads to a reduction in the amount of water entering the connecting pipe 34 at the lower position. Combined with Figure 5 Since the second tube body 42 is the water inlet end, when the second tube body 42 is at a lower position, the gravity of the fluid in the first tube body 41 causes a certain resistance to the rotation. Therefore, by reducing the water inflow when the second tube body 42 is at a lower position, a flow difference is formed in the two second tube bodies 42, and the rotation resistance caused by the gravity of the fluid in the second tube body 42 on the lower side is reduced, so as to better promote the overall rotation.

[0090] At a fermentation temperature of 20°C, the yeast inoculation concentration was 4×10 6 / mL, the initial actual alcohol content of the original wine is 5%vol, and the initial sugar content is 17mg / L under the secondary fermentation conditions, batch secondary fermentation rice wine production is carried out according to the method in Example 1 and using traditional fermentation equipment. It is actually measured that after fermentation, the average purine content in the secondary fermentation finished wine is 2.3mg / L. In the process of using the fermentation equipment in this embodiment and carrying out batch fermentation for the same number of times according to the aforementioned method, the temperature is controlled by passing water through the cooling pipeline after the temperature inside the fermentation tank 1 is increased. During the water circulation process, the combined pipe 4 is driven to generate rotation and stirring, which accelerates the diffusion of heat and reduces the temperature difference between local areas in the fermentation tank 1. Batch secondary fermentation rice wine production is carried out using the fermentation equipment in Example 2, and the average purine content in the finished wine after fermentation is 2.15mg / L. It can be seen that compared with the use of the traditional fermentation equipment in Example 1, the use of the fermentation equipment in Example 2 reduces the purine content of the secondary fermentation finished wine.

[0091] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A secondary fermentation process for yellow rice wine, characterized in that: The steps include: S1: Screening yeast ① Filter grape juice from grapes and ferment it to obtain various yeasts; ② Cultivate multiple yeasts in culture medium; ③ Use finished rice wine and water to mix to obtain raw wine; ④ Extract various yeasts and add them into the original wine for fermentation test; ⑤ Detect the purine content of the original liquor after fermentation with different yeast species; S2: Secondary fermentation The yeast with low purine content after fermentation obtained in step S1 ④ is used to ferment the base liquor prepared in step S1 ③.

2. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: In step S1 ③, the alcohol content of the blended base liquor is 5% vol-6% vol, and the glucose content is 16 g / L-19 g / L.

3. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: The fermentation test temperature in step S1 ④ is 15°C-30°C.

4. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: In S2, during fermentation, the yeast inoculation concentration was 4×10 5 / mL-4×10 7 pieces / mL.

5. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: The fermentation temperature in S2 is controlled at 15°C-30°C.

6. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: In S2, fermentation under pressure was used.

7. The secondary fermentation process of yellow rice wine according to claim 1, characterized in that: In step ② of S1, the culture medium is prepared as follows: ① Prepare TTC lower layer medium: Dissolve 4g-5.05g glucose, 0.8g-1.2g peptone, 0.65-0.8g yeast extract, 0.4g-0.55g potassium dihydrogen phosphate, 0.15g-0.25g magnesium sulfate, 0.1g-0.15g citric acid, and 8g-12g agar in 500mL of distilled water. Sterilize with high pressure steam and pour onto plates to obtain TTC lower layer medium. Confirm sterility by blank culture at 25°C-28°C. ② Dilute the fermented grape juice with sterile water to culture yeast; ③ Prepare TTC top culture medium: Weigh 2.5g-3.5g glucose and 2g-3g agar and dissolve them in 100ml water. Heat to dissolve and sterilize with high-pressure steam. Aseptically add 0.025g-0.03g TTC bottom culture medium in a water bath at 45℃-50℃. After dissolution, pour the culture medium into a plate and incubate at 25℃-30℃ in the dark. Then, inoculate the TTC top culture medium into 12°BX malt wort using an inoculation loop and incubate at a constant temperature of 25℃-30℃ for 18-25 hours.

8. The secondary fermentation process of yellow rice wine according to claim 7, characterized in that: In step ② of preparing the culture medium, the method for diluting the cultured yeast is: Take 1 dose of fermented grape juice and put it into a test tube with 9 doses of sterile water and shake it well, which is 10. -1 Tube; From 10 -1 One dose is drawn from the tube and placed in 9 doses of sterile water test tubes, which is counted as 10 -2 Tube; Prepare 10 in the same way -3 Tube, 10 -4 Tube, 10 -5 Tube, 10 -6 Tube, 10 -7 Tube, 10 -8 Tube; The diluted bacterial solution in the test tube was inoculated into sterile culture dishes containing TTC lower culture medium that had been blank cultured, spread evenly, and cultured in a biochemical incubator at 25℃-30℃ for 2-3 days.

9. The secondary fermentation process of yellow rice wine according to claim 8, characterized in that: The 1 dose is 1 ml.

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