Fermented wine rich in mellow and sweet taste and preparation process thereof

Abstract

According to the fermented wine rich in alcohol and sweetness and the preparation process thereof, high-sugar-degree grain liquid (wort) is adopted as a fermentation substrate, fermentation is controlled through functional strains in a labor division and staged mode, and the technical problems that in a traditional process, glycerol synthesis is limited, and a wine body is thin, sour and astringent are effectively solved. The content of glycerol is increased under the pure fermentation condition, meanwhile, the content of by-products such as residual sugar and acetic acid is reduced, and high alcoholic sweetness and wine flavor coordination are synchronously achieved in a pure biological fermentation framework.

Description

Technical Field

[0001] This invention belongs to the field of brewing technology, specifically relating to a fermented wine rich in mellow sweetness and its preparation process. Background Technology

[0002] Currently, commercially available fermented alcoholic beverages (such as dry wines, fruit wines, and sake) generally contain glycerol (glycerol) in the range of 5–15 g / L. Its production primarily depends on the secondary metabolism of brewer's yeast during alcoholic fermentation. Traditional processes employ a single-strain, single-stage fermentation model, where yeast produces only trace amounts of glycerol to balance osmotic pressure while converting sugar into ethanol. Although some studies have attempted to increase glycerol production by adding sulfites, adjusting the sugar-acid ratio, or screening wild-type strains, the practical effects are limited due to a lack of systematic regulation: firstly, the activity of glycerol synthases (such as GPD1) in the strains is inhibited by ethanol feedback, leading to a sharp drop in yield in the mid-to-late stages; secondly, nitrogen sources supplemented to maintain yeast activity (such as diammonium hydrogen phosphate) may accelerate alcoholic fermentation, conversely inhibiting glycerol accumulation. Such technologies struggle to overcome the dual bottleneck of glycerol content and the balance between alcohol content and body composition.

[0003] Existing low-glycerol fermented spirits produced using current processes exhibit significant tasting defects: a thin body and prominent acidity and astringency, especially noticeable in low-alcohol (<11% vol) products. To mask these defects, some manufacturers add exogenous glycerol or sweeteners later in the fermentation process. However, this not only violates regulations for pure fermented spirits but also results in an artificially sweet and cloying taste, and a fragmented flavor profile. Meanwhile, the trend towards health-conscious consumption has created a demand for "low-intensity, high-body" spirits—consumers expect a smooth, sweet taste from natural fermentation, without added sugar or artificial flavorings. However, current technology cannot stably increase glycerol to above the functional threshold of 30g / L while maintaining the pure fermentation properties. This contradiction highlights the industry's urgent need for innovative fermentation processes that selectively enrich sweet substances without relying on additives. Summary of the Invention

[0004] The purpose of this invention is to provide a fermented wine rich in mellow sweetness and its preparation process. This process is a staged dual-strain fermentation process that uses high-sugar grain liquid as the fermentation base. Through the division of labor among functional strains, fermentation is controlled in stages, effectively solving the technical problems of limited glycerol synthesis and thin, sour body in traditional processes. It achieves the goal of increasing the content of glycerol under pure fermentation conditions, while reducing the content of defective by-products such as residual sugar and acetic acid. It simultaneously achieves high mellow sweetness and harmonious flavor of the wine within the framework of pure biological fermentation.

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

[0006] A process for preparing a fermented wine rich in mellow sweetness includes the following steps:

[0007] Step 1): Select a high-osmotic fermentation substrate and sterilize it;

[0008] Step 2): Select the functional strain *Candida krusei* 31750) and Saccharomyces cerevisiae Y1 were activated separately;

[0009] Step 3): Place the hyperosmolar fermentation substrate in a fermentation vessel. In the initial stage of fermentation, inoculate 5-10% (v / v) of Candida crocetamol for the first stage of fermentation. The fermentation temperature is 18-22℃, pH is 3.4-4.5, DO is 5-15%, and the fermentation time is 96-120 hours. In this stage, the carbon source is converted into glycerol via the DHAP pathway. When the glycerol concentration reaches 30 g / L, the first stage of fermentation ends. Inactivate Candida crocetamol using pasteurization, and then inoculate 3-5% (v / v) of Saccharomyces cerevisiae Y1 for the second stage of fermentation. The temperature is 25-28℃, pH is 3.2-3.8, and the system is switched to an anaerobic state. The fermentation time is 120 hours, driving the sugar metabolism to shift to ethanol as the main fermentation process.

[0010] Preferably, in step 1), the hyperosmotic fermentation substrate is a malt wort fermentation substrate with a sugar content of 30°Bx. Using a malt wort fermentation substrate with a sugar content of 30°Bx creates hyperosmotic fermentation conditions, forcing yeast to initiate the glycerol synthesis pathway to balance the osmotic pressure.

[0011] Preferably, the sterilization process in step 1) involves sterilizing the hyperosmolar fermentation substrate with high-pressure steam at 0.12 MPa for 20 minutes.

[0012] Preferably, in step 2), *Candida croceta* is activated to a viable count ≥ 1 × 10⁸ CFU / mL; and *Saccharomyces cerevisiae* Y1 is activated to a viable count ≥ 2 × 10⁸ CFU / mL.

[0013] Preferably, after the first stage of fermentation in step 3) is completed, *Candida croceta* is inactivated, and the fermentation broth is centrifuged to obtain a glycerol-rich fermentation broth.

[0014] Preferably, in step 3), pasteurization is performed at 70°C for 10 minutes.

[0015] The present invention also provides a fermented wine prepared by the above method, wherein the glycerol content in the fermented wine is above 30 g / L, preferably above 34 g / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention uses high-sugar grain liquid (malt extract) as the fermentation base. Through the division of labor among functional strains and the phased control of fermentation, it effectively solves the technical problems of limited glycerol synthesis and thin, sour body in traditional processes. It achieves the increase of glycerol content under pure fermentation conditions, while reducing the content of by-products such as residual sugar and acetic acid. It simultaneously achieves high alcohol sweetness and harmonious flavor of the wine within the framework of pure biological fermentation. Detailed Implementation

[0018] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0019] Example 1: Effects of sugar content / dissolved oxygen / pH on glycerol yield

[0020] Sugar content, dissolved oxygen, and pH were selected as the three factors required for the experiment. Candida klure was inoculated at 5% (v / v) in malt extract for fermentation. An L9(34) orthogonal array was used to investigate the three factors at three levels. See Table 1:

[0021] Table 1

[0022]

[0023] The first stage of fermentation was conducted at a temperature of 20℃ under microaerobic conditions (DO 10%) for 120 hours. After fermentation, the fermentation broth was centrifuged to obtain a glycerol-rich broth, which was then inoculated with *Saccharomyces cerevisiae* Y1 at 3% (v / v) and fermented for 18 hours under anaerobic conditions. The results of each group of experiments are shown in Table 2.

[0024] Table 2

[0025]

[0026] According to the statistical results in Table 2, when the optimal combination is 30°Bx sugar content, 15% dissolved oxygen, and pH 3.5, the glycerol content reaches 36.2 g / L, and the glycerol / ethanol ratio reaches a maximum of 5.57. At 30°Bx, the glycerol yield is on average 18.7% higher than at 25°Bx and 35°Bx; at 15% dissolved oxygen, the glycerol yield is 24.3% higher than at 5% dissolved oxygen; and at pH ≤ 3.5, the acetic acid content decreases by 63%.

[0027] Example 2: Scaled-up Production Verification

[0028] 1. Materials and Equipment

[0029] Fermentation base: barley malt extract (saccharide content 30°Bx, sterilized at 0.12 MPa for 20 min)

[0030] Strain: Candida krusei 31750), commercially acquired, activated to a viable count ≥1×10⁸ CFU / mL; Saccharomyces cerevisiae Y1 activated to a viable count ≥2×10⁸ CFU / mL. The preservation number of Saccharomyces cerevisiae Y1 is CCTCC NO: M 20241943, recorded in CN119410504A, acquired by Kingboard Holdings Limited.

[0031] Equipment: 10L stainless steel fermentation tank (equipped with dissolved oxygen probe, online pH monitoring, and temperature control system).

[0032] 2. Control of key process parameters

[0033] This embodiment guides the yeast's metabolic pathway conversion through precise control of environmental parameters to produce the target product in stages. The first stage (glycerol synthesis) is carried out for 120 hours under aerobic conditions of low temperature (20°C), low pH (3.5), and high dissolved oxygen (15%), which promotes the preferential conversion of carbon sources into glycerol and the accumulation of biomass. Subsequently, the second stage (ethanol synthesis) is initiated by rapidly increasing the temperature (26°C), slightly decreasing the pH (3.2), and creating a strictly anaerobic environment (dissolved oxygen ≤0.5%), forcing the yeast to switch to an anaerobic fermentation mode, and efficiently converting the remaining sugars into ethanol within 96 hours.

[0034] For ease of comparison, this embodiment also utilizes conventional fermentation processes to prepare the wine. Malt extract is used as the raw material, pasteurized and cooled, then inoculated with the same single brewing yeast strain as in this embodiment. Primary fermentation is carried out at a constant temperature of 22°C until the end of fermentation (fermentation cycle is 7 days), without segmented temperature control or nutrient supplementation during this period. After fermentation, the final product is obtained after conventional treatments such as centrifugation and filtration.

[0035] 3. Results and Sensory Evaluation

[0036]

[0037] This embodiment verified the feasibility of the process on a 10L scale, with a glycerol content of 34.7g / L, a residual sugar content of only 9g / L, and an acetic acid content of only 0.41g / L, resulting in a wine with significant advantages in sweetness and balance.

[0038] The above description is merely a specific embodiment of this application and is not intended to limit this application. For those skilled in the art, this application can have various changes and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A process for preparing a fermented wine rich in mellow sweetness, characterized in that, Includes the following steps: Step 1): Select a high-osmotic fermentation substrate and sterilize it; Step 2): Select the functional strain *Candida krusei* 31750) and brewer's yeast Y1 were activated separately; Step 3): Place the hyperosmolar fermentation substrate in a fermentation vessel. In the initial stage of fermentation, inoculate 5-10% (v / v) of Candida crocetamol for the first stage of fermentation. The fermentation temperature is 18-22℃, pH is 3.4-4.5, DO is 5-15%, and the fermentation time is 96-120 hours. In this stage, the carbon source is converted into glycerol via the DHAP pathway. When the glycerol concentration reaches 30 g / L, the first stage of fermentation ends. Inactivate Candida crocetamol using pasteurization, and then inoculate 3-5% (v / v) of Saccharomyces cerevisiae Y1 for the second stage of fermentation. The temperature is 25-28℃, pH is 3.2-3.8, and the system is switched to an anaerobic state. The fermentation time is 120 hours, driving the sugar metabolism to shift to ethanol as the main fermentation process.

2. The preparation process according to claim 1, characterized in that, In step 1), the hyperosmolar fermentation substrate is a malt extract fermentation substrate with a sugar content of 30°Bx.

3. The preparation process according to claim 1, characterized in that, The sterilization process described in step 1) involves sterilizing the hyperosmolar fermentation substrate with high-pressure steam at 0.12 MPa for 20 minutes.

4. The preparation process according to claim 1, characterized in that, In step 2), *Candida croceta* is activated to a viable count ≥ 1 × 10⁸ CFU / mL; *Saccharomyces cerevisiae* Y1 is activated to a viable count ≥ 2 × 10⁸ CFU / mL.

5. The preparation process according to claim 1, characterized in that, After the first stage of fermentation in step 3) is completed, Candida croceta is inactivated, and the fermentation broth is centrifuged to obtain a glycerol-rich fermentation broth.

6. The preparation process according to claim 1, characterized in that, In step 3), pasteurize at 70°C for 10 minutes.

7. A fermented wine prepared using the process described in any one of claims 1-6, characterized in that, The glycerol content in fermented wine is above 30g / L.

8. The fermented wine according to claim 7, characterized in that, The glycerol content in fermented wine is above 34g / L.

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