Production process for preparing sweet white wine by denitrification method

Abstract

This invention discloses a denitrification process for preparing sweet white wine. The process steps are as follows: Grape pretreatment: Select fresh white grapes of uniform ripeness, manually remove rotten and diseased grapes, destem, crush, and extract juice using a press. Collect the juice and filter to remove pomace to obtain initial grape juice; Juice clarification: Quickly cool the initial grape juice to 3-5°C, add 30-35 mg / L pectinase and 40-60 mg / L sulfur dioxide, stir evenly, and let it stand for clarification for 24-36 hours. Take the supernatant as the fermentation liquid; Primary denitrification fermentation: Transfer the fermentation liquid to a fermentation tank, raise the temperature to 12-15°C, inoculate with wine yeast, control the fermentation temperature at 16-18°C, and stir 2-3 times a day; When the alcohol content of the fermentation liquid reaches 3.5% vol, add 0.4-0.5 g / L of chitosan-benzene complex. This invention's staged denitrification avoids the yeast stress response caused by adding a large amount of adsorbent at once, and significantly enhances the microbial stability of the wine.

Description

Technical Field

[0001] This invention relates to the field of white wine production technology, specifically a denitrification method for preparing sweet white wine. Background Technology

[0002] Sweet white wines, with their refreshing fruit aromas and balanced sweet and sour taste, are beloved by consumers worldwide, especially in markets like Asia and North America where demand continues to grow. As consumers become more health-conscious, low-sulfur, natural, and high-quality sweet white wines are gradually becoming the market mainstream. However, the traditional sweet white wine production process faces several technological bottlenecks. Traditional sweet white wine production typically uses a "freezing + sulfur dioxide" method to stop fermentation in order to retain residual sugar. This process has the following core problems:

[0003] 1. Sulfur dioxide residue problem: In order to inhibit yeast activity, a large amount of sulfur dioxide needs to be added, resulting in excessive sulfur dioxide content in the finished wine. This not only affects the taste, but may also trigger allergic reactions, which is not in line with the trend of healthy consumption.

[0004] 2. Risk of secondary fermentation: The high sugar environment of sweet wines can easily cause residual yeast to reactivate during storage, triggering secondary fermentation, which can cause the wine to become cloudy, increase the pressure inside the bottle, and seriously affect the product stability and shelf life.

[0005] 3. Flavor Loss: During the freezing process to terminate fermentation, the low temperature destroys some aroma compounds, and the oxidation of sulfur dioxide reduces the intensity of fruit aromas, resulting in a one-dimensional flavor and a lack of complexity in the wine. High Process Complexity: Traditional processes require strict control of freezing temperature and time, and multiple filtrations and clarifications are necessary, leading to long production cycles, high costs, and hindering large-scale production.

[0006] Limitations of Existing Nitrogen Removal Fermentation Technologies: To address the shortcomings of traditional processes, some studies have attempted to terminate fermentation using nitrogen removal methods, inhibiting yeast activity by adsorbing essential nitrogen sources. Current technologies primarily employ single-component bentonite nitrogen removal, which has the following drawbacks:

[0007] 1. Low nitrogen removal efficiency: Single-origin bentonite lacks selectivity in adsorbing nitrogen sources and easily adsorbs aroma components simultaneously, leading to significant loss of fruity aroma. Fermentation control is difficult.

[0008] 2. Existing technologies often employ two-stage denitrification processes, making it difficult to precisely control the rate of yeast activity decline, which can easily lead to fermentation stagnation or over-fermentation. This results in poor wine stability.

[0009] 3. If the wine is not completely cleaned after single clay treatment, protein turbidity may occur during storage, affecting product quality.

[0010] To address the aforementioned technical challenges, this invention proposes a novel denitrification process for preparing sweet white wine, building upon existing denitrification fermentation technologies. It innovatively employs a three-stage gradient denitrification strategy, combined with chitosan-benzene composite adsorbent materials, to achieve precise control of the fermentation process and enhance flavor and quality. Summary of the Invention

[0011] The purpose of this invention is to provide a process for preparing sweet white wine using a nitrogen removal method, the process steps of which are as follows:

[0012] Step 1: Grape pretreatment: Select fresh white grapes with uniform ripeness, manually remove rotten and diseased grapes, destem, crush and break them, then use a press to extract the juice, collect the juice and filter to remove the pulp to obtain the initial grape juice;

[0013] Step 2: Juice clarification: Quickly cool the initial grape juice to 3-5℃, add 30-35mg / L pectinase and 40-60mg / L sulfur dioxide, stir well and let stand for clarification for 24-36 hours, and take the supernatant as the fermentation liquid;

[0014] Step 3: First-stage denitrification fermentation: Transfer the fermentation liquid to a fermentation tank, heat to 12-15℃, inoculate with brewing yeast, control the fermentation temperature at 16-18℃, and stir 2-3 times a day; when the alcohol content of the fermentation liquid reaches 3.5% vol, add 0.4-0.5 g / L of chitosan-saponin complex, stir evenly, let stand for 6-8 hours, remove the flocculent precipitate at the bottom of the tank, and continue fermentation;

[0015] Step 4: Secondary denitrification fermentation: When the alcohol content of the fermentation broth reaches 5.5% vol, add 0.6-0.7 g / L of chitosan-saponin complex again, stir evenly, let stand for 8-10 hours, remove the precipitate, and continue fermentation;

[0016] Step 5: Three-stage denitrification fermentation: When the alcohol content of the fermentation broth reaches 7.0% vol, add 0.8-0.9 g / L of chitosan-benzene complex, stir evenly, and let stand for 10-12 hours to remove the precipitate; continue to control the temperature at 16-18℃ for 20-28 hours of fermentation, until the alcohol content reaches 10-12% vol, then quickly cool down to 1-2℃, centrifuge to remove the lees precipitate, and collect the supernatant;

[0017] Step 6: Bottling: Transfer the supernatant to a storage tank and age it at 1-2℃ for 30-60 days, changing the tank every 10 days during this period. After aging, filter it sterilely, fill it into sterile glass bottles, and seal it to obtain the finished sweet white wine.

[0018] Preferably, the pressing pressure of the press is controlled at 0.2 to 0.3 MPa, and the juice temperature does not exceed 10°C during the juicing process.

[0019] Preferably, the pectinase has an enzyme activity ≥10000u / g.

[0020] Preferably, the brewing yeast is active dry yeast, which needs to be activated with a 5% glucose solution at 20-25°C for 30-45 minutes before inoculation, and the inoculation amount of brewing yeast is 106-107 CFU / mL.

[0021] Preferably, the chitosan-benzene composite has a chitosan to bentonite mass ratio of 1:4.

[0022] Preferably, in step 6, the sterilization filtration uses a 0.22μm microporous filter membrane, and nitrogen protection is used during the bottling process to prevent the wine from coming into contact with air.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention employs a three-stage gradient denitrification strategy, sequentially adding chitosan-benzene complexes at three key points: 3.5% vol, 5.5% vol, and 7.0% vol. This gradually reduces the α-amino nitrogen content in the fermentation broth, causing yeast activity to decline in a gradient manner. Ultimately, the yeast naturally enters a dormant state at an alcohol content of 10–12% vol. This precise control of nitrogen supply during fermentation effectively solves the problems of easy fermentation stagnation and large fluctuations in residual sugar in traditional sweet wines. At the same time, the staged denitrification avoids the yeast stress response caused by adding a large amount of adsorbent at once, significantly enhancing the microbial stability of the wine.

[0025] This invention uses a composite adsorbent material with a chitosan and bentonite mass ratio of 1:4. This material retains the high adsorption capacity of bentonite for proteins and peptides, while reducing the non-specific adsorption of aromatic substances through the specific binding effect of chitosan, thus significantly enhancing the richness and freshness of the fruit aroma.

[0026] The process of this invention does not require the addition of additional chemical reagents to terminate fermentation, and the total amount of sulfur dioxide used is significantly reduced compared to the traditional freezing + SO2 termination method, which is in line with the consumption trend of low sulfur and natural products. The precipitates generated during the segmented denitrification process can be removed by simple filtration without the need for complex centrifugation equipment, thus reducing equipment investment costs. At the same time, the fermentation cycle is shortened compared to the traditional process, improving production efficiency. Attached Figure Description

[0027] Figure 1 is a flowchart of the steps of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] As attached Figure 1 As shown, the present invention provides a process for preparing sweet white wine using a nitrogen removal method. The process steps are as follows:

[0030] Step 1: Grape pretreatment: Select fresh white grapes with uniform ripeness, manually remove rotten and diseased grapes, destem, crush and break them, then use a press to extract the juice, collect the juice and filter to remove the pulp to obtain the initial grape juice;

[0031] Step 2: Juice clarification: Quickly cool the initial grape juice to 3-5℃, add 30-35 mg / L pectinase and 40-60 mg / L sulfur dioxide, the enzyme activity of the pectinase is ≥10000u / g, stir evenly and let stand to clarify for 24-36 hours, and take the supernatant as the fermentation liquid.

[0032] Step 3: First-stage denitrification fermentation: Transfer the fermentation liquid to a fermentation tank, heat to 12-15℃, inoculate with brewing yeast, control the fermentation temperature at 16-18℃, and stir 2-3 times a day; when the alcohol content of the fermentation liquid reaches 3.5% vol, add 0.4-0.5 g / L of chitosan-saponin complex, stir evenly, let stand for 6-8 hours, remove the flocculent precipitate at the bottom of the tank, and continue fermentation;

[0033] Step 4: Secondary denitrification fermentation: When the alcohol content of the fermentation broth reaches 5.5% vol, add 0.6-0.7 g / L of chitosan-saponin complex again, stir evenly, let stand for 8-10 hours, remove the precipitate, and continue fermentation;

[0034] Step 5: Three-stage denitrification fermentation: When the alcohol content of the fermentation broth reaches 7.0% vol, add 0.8-0.9 g / L of chitosan-benzene complex, stir evenly, and let stand for 10-12 hours to remove the precipitate; continue to control the temperature at 16-18℃ for 20-28 hours of fermentation, until the alcohol content reaches 10-12% vol, then quickly cool down to 1-2℃, centrifuge to remove the lees precipitate, and collect the supernatant;

[0035] Step 6: Bottling: Transfer the supernatant to a storage tank and age it at 1-2℃ for 30-60 days, changing the tank every 10 days during this period. After aging, filter the wine through a 0.22μm microporous membrane for sterilization, and fill it into sterile glass bottles under nitrogen protection. Seal the bottles to obtain the finished sweet white wine.

[0036] Specifically, the pressing pressure of the press is controlled at 0.2 to 0.3 MPa, and the juice temperature does not exceed 10°C during the juicing process.

[0037] Specifically, the brewing yeast is an active dry yeast, which needs to be activated with a 5% glucose solution at 20-25℃ for 30-45 minutes before inoculation. The inoculation amount of brewing yeast is 106-107 CFU / mL.

[0038] Specifically, chitosan is dissolved in a 1% acetic acid solution to prepare a 2% solution by mass, which is then mixed with a 5% bentonite suspension at a mass ratio of 1:4. After stirring and reacting for 30 minutes, the mixture is spray-dried to obtain a powdered composite.

[0039] Any technical solution that achieves the above-mentioned technical effects by utilizing the technical solutions described in this invention, or by designing similar technical solutions by those skilled in the art under the inspiration of the technical solutions described in this invention, falls within the protection scope of this invention.

Claims

1. A process for preparing sweet white wine using a nitrogen removal method, characterized in that: The process steps are as follows: Step 1: Grape pretreatment: Select fresh white grapes with uniform ripeness, manually remove rotten and diseased grapes, destem, crush and break them, then use a press to extract the juice, collect the juice and filter to remove the pulp to obtain the initial grape juice; Step 2: Juice clarification: Quickly cool the initial grape juice to 3-5℃, add 30-35mg / L pectinase and 40-60mg / L sulfur dioxide, stir well and let stand for clarification for 24-36 hours, and take the supernatant as the fermentation liquid; Step 3: First-stage denitrification fermentation: Transfer the fermentation liquid to a fermentation tank, heat to 12-15℃, inoculate with brewing yeast, control the fermentation temperature at 16-18℃, and stir 2-3 times a day; when the alcohol content of the fermentation liquid reaches 3.5% vol, add 0.4-0.5 g / L of chitosan-saponin complex, stir evenly, let stand for 6-8 hours, remove the flocculent precipitate at the bottom of the tank, and continue fermentation; Step 4: Secondary denitrification fermentation: When the alcohol content of the fermentation broth reaches 5.5% vol, add 0.6-0.7 g / L of chitosan-saponin complex again, stir evenly, let stand for 8-10 hours, remove the precipitate, and continue fermentation; Step 5: Three-stage denitrification fermentation: When the alcohol content of the fermentation broth reaches 7.0% vol, add 0.8-0.9 g / L of chitosan-benzene complex, stir evenly, and let stand for 10-12 hours to remove the precipitate; continue to control the temperature at 16-18℃ for 20-28 hours of fermentation, until the alcohol content reaches 10-12% vol, then quickly cool down to 1-2℃, centrifuge to remove the lees precipitate, and collect the supernatant; Step 6: Bottling: Transfer the supernatant to a storage tank and age it at 1-2℃ for 30-60 days, changing the tank every 10 days during this period. After aging, filter it sterilely, fill it into sterile glass bottles, and seal it to obtain the finished sweet white wine.

2. The production process for preparing sweet white wine by nitrogen removal method according to claim 1, characterized in that: The pressing pressure of the press is controlled at 0.2 to 0.3 MPa, and the juice temperature does not exceed 10°C during the juicing process.

3. The production process for preparing sweet white wine by nitrogen removal method according to claim 1, characterized in that: The pectinase has an enzyme activity ≥10000u / g.

4. The production process for preparing sweet white wine by nitrogen removal method according to claim 1, characterized in that: The brewing yeast is an active dry yeast, which needs to be activated with a 5% glucose solution at 20-25℃ for 30-45 minutes before inoculation. The inoculation amount of brewing yeast is 10... 6 ~10 7 CFU / mL.

5. The production process for preparing sweet white wine by nitrogen removal method according to claim 1, characterized in that: The chitosan-benzene composite has a chitosan to bentonite mass ratio of 1:

4.

6. The production process for preparing sweet white wine by nitrogen removal according to claim 1, characterized in that: In step 6, a 0.22μm microporous membrane is used for sterilization filtration, and nitrogen protection is used during the bottling process to prevent the wine from coming into contact with air.

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