A microbial enrichment mash for improving the fermentation speed and sensory quality of natural fermentation red wine, and a preparation method and application thereof

Abstract

The application discloses a kind of microbial enrichment mash for improving the fermentation speed and sensory quality of natural fermentation red wine and its preparation method and application, it is related to wine preparation technical field, specifically includes the following steps: (1) after the mature wine grape is removed stem, broken and beaten, grape mash is obtained;(2) the grape mash is oxygenated and then subjected to multi-stage gradient enrichment culture;Wherein, the method for multi-stage gradient enrichment culture is as follows: after the grape mash is cultured at 12-14 DEG C for 18-30 h, the temperature is increased to 18-20 DEG C and cultured for 18-30 h, and finally the temperature is increased to 24-26 DEG C and cultured for 18-30 h.The method of the application can solve the problem of slow fermentation speed and certain degree of undesirable flavor of natural fermentation red wine, shorten the brewing cycle of natural fermentation red wine, and help improve the sensory quality.

Description

Technical Field

[0001] This invention relates to the field of wine preparation technology, specifically to a microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine, its preparation method, and its application. Background Technology

[0002] Naturally fermented wine is generally considered to be a type of wine made using the grapes' own microorganisms without the addition of commercial fermentation agents, fermentation nutrient supplements, SO2, tartaric acid, or other exogenous auxiliary materials during the winemaking process, thus possessing the characteristics of the wine region's terroir. As the concepts of additive-free, pollution-free, and green food gain popularity, and consumers demand innovative wine styles, the concept of sustainable development in wine production brings new opportunities and challenges to the wine industry. Naturally fermented wine, with its additive-free nature and unique "terroir" characteristics, is favored by consumers and has a potential consumer market.

[0003] For a long time, "terroir" has been a hot topic in the wine industry. The concept of "terroir," originating in France, primarily refers to wines that are distinctive, of exceptional quality, and unique, reflecting a close connection to the land. It is a unique, intangible regional resource, meaning the sum of environmental factors influencing grape growth—geographical location, topography, soil type, sunlight conditions, rainfall, diurnal temperature variation, and environmental microorganisms—all natural factors that influence the style of wine. True "terroir" gives wine its "soul." Currently, the analysis of wine "terroir" is becoming increasingly in-depth and expanded, with microbial "terroir" becoming the core of discussions about overall "terroir." This describes how vineyard microorganisms are unique and influence the characteristics and style of wine in specific ways, making them an important component in expressing the quality of the wine.

[0004] In summary, the "terroir" of microorganisms possesses distinct regional, spatial, and temporal characteristics, which better highlight the unique features of wine regions and grape varieties. Therefore, natural fermentation can produce complex and distinctive wines with regional characteristics, showcasing the wine's regional style. However, natural fermentation also brings unpredictable risks to the winemaking process. Related research has found that the slow rate of natural fermentation can lead to the proliferation of harmful microorganisms, generating undesirable flavors such as stable or leathery notes, or high volatile acids, and even producing toxic substances. Furthermore, raw materials with potentially high ethanol volumes may not undergo complete natural fermentation. These are all issues that must be addressed. For example, red wine is made from red grapes that have been destemmed, crushed, and fermented with their skins on. The surface of the grapes is a natural carrier of microorganisms, which mix with the grape skins in the must and participate in the fermentation process. Therefore, naturally fermented red wines are more prone to the aforementioned problems.

[0005] Therefore, providing a brewing method to improve the fermentation speed and sensory quality of naturally fermented red wine is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine, along with its preparation method and application. This method can solve the problems of slow fermentation speed and certain undesirable flavors in naturally fermented red wine, shorten the brewing cycle of naturally fermented red wine, and help improve its sensory quality.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing microbially enriched mash to improve the fermentation speed and sensory quality of naturally fermented red wine includes the following specific steps:

[0009] (1) Grape must is obtained by destemming, crushing and pulping mature wine grapes;

[0010] (2) The grape must is oxygenated, and after oxygenation, it is subjected to multi-level gradient enrichment culture. Then, the grape must after culture is separated to obtain free-flowing must and pomace. The pomace is pressed to obtain pressed must. The pressed must and the free-flowing must are mixed to obtain microbial enriched must.

[0011] The multi-level gradient enrichment culture method is as follows: after culturing the grape must at 12-14℃ for 18-30h, the temperature is raised to 18-20℃ for 18-30h, and finally raised to 24-26℃ for 18-30h.

[0012] In the winemaking process, strengthening the growth and control of microorganisms in key stages is crucial for the successful completion of the entire fermentation process. This involves not only optimizing wine yeast but also controlling the growth of harmful yeasts or bacteria. Therefore, appropriate measures should be taken during the winemaking process to minimize microbial contamination. In conventional winemaking, microbial control can be achieved through chemical additives (preservatives and bactericides) and physical sterilization. However, these methods cannot be used in natural winemaking. The natural microorganisms on the surface of grapes are complex, and the interactions between different microorganisms are a significant factor affecting wine fermentation. The optimal culture temperature for yeast is 24-28℃, and for bacteria, it is 35-38℃. In the high-temperature, high-sugar grape must, both bacteria and yeast easily multiply and proliferate. However, their reproduction rates differ at different temperatures. At lower temperatures, superior, dominant yeasts can still maintain a certain growth rate, while bacteria grow relatively slowly. Therefore, the proportion of superior, dominant yeasts gradually increases, while the proportion of harmful bacteria gradually decreases. Furthermore, the gradual, multi-gradient heating not only ensures the increasing proportion of dominant yeasts but also effectively improves their enrichment culture efficiency. Therefore, by employing multi-level gradient enrichment culture and a gradual heating trend, this invention can provide suitable culture conditions for the growth of naturally dominant microorganisms, effectively preventing the growth of harmful bacteria. It can also enable the grape's own dominant and beneficial microorganisms to proliferate rapidly in a short period of time, reducing the abundance or proportion of harmful microorganisms and improving the efficiency of enrichment culture. Thus, it can effectively improve the initiation speed and fermentation quality of natural red wine alcoholic fermentation.

[0013] This invention uses red grape varieties as a natural substrate to capture and enrich the natural microorganisms on the grape skin, obtaining a naturally enriched microbial canister. This canister is then used as a natural microbial fermentation agent for naturally fermented red wine, enabling the red grape canister to be inoculated with more beneficial, dominant, and distinctive fermentation microbial populations, significantly improving the quality of naturally fermented red wine.

[0014] Preferably, the wine grapes used in step (1) are fresh, disease-free, rotten, moldy, and unripe red wine grape varieties.

[0015] Preferably, the red grape variety is any one of Cabernet Sauvignon, Merlot, Pinot Noir, Marselan, Cabernet Gernischt, and Syrah.

[0016] Preferably, the temperature of the grape must obtained after pulping is controlled at 16-18℃.

[0017] Preferably, the oxygenation amount in step (2) is 8-10 mg / L, and the temperature of the oxygenated grape must is <7°C.

[0018] Preferably, the microbial enrichment mash is cooled to 0-2°C and stored for later use.

[0019] Preferably, the microbial enrichment mash is cooled to 1°C and stored for later use.

[0020] In order to improve the stability of naturally enriched grape must, this invention requires low-temperature storage of the grape must. Under low-temperature conditions, the microorganisms are in a dormant state and their reproduction and metabolism are weak. Therefore, it can effectively maintain the stability of the number and proportion of microorganisms in the must and ensure that the inoculation requirements for the production of naturally fermented red wine are met.

[0021] A microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine was obtained according to the preparation method described above.

[0022] The above-described application of microbially enriched mash in the brewing of naturally fermented red wine.

[0023] Preferably, the brewing process specifically includes:

[0024] 1) After destemming, crushing and pulping ripe wine grapes, fermented grape must is obtained;

[0025] 2) After inoculating the fermented grape must with the microbial enrichment, the wine is then subjected to alcoholic fermentation and malolactic fermentation in sequence to obtain naturally fermented red wine.

[0026] Preferably, the wine grapes mentioned in step 1) are fresh, disease-free, rotten, moldy, and unripe grapes of the same variety as the raw materials for microbial enrichment of the must.

[0027] Preferably, the inoculum amount of the microbial enrichment mash in step 2) is 2-4 wt%.

[0028] Preferably, the specific steps of alcoholic fermentation in step 2) are as follows: natural fermentation is carried out at 24-26℃, and the specific gravity and temperature of the fermented grape must are measured at intervals every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness, and the alcoholic fermentation is ended. The skins and pomace are separated to obtain naturally fermented red grape wine. The alcoholic fermentation can realize the microbial flavor metabolism of naturally fermented red wine, which satisfies the basic flavor profile and style characteristics of the wine.

[0029] The specific steps of the malolactic fermentation are as follows: the naturally fermented red grape wine is naturally fermented at 22-24℃. When no malic acid is detected by malic acid paper chromatography, the malolactic fermentation is considered to be over, and the naturally fermented red wine is obtained. The malolactic fermentation can improve the stability, flavor and taste of the wine, and helps to obtain a naturally fermented red wine with stable quality.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The method of this invention can solve the problems of slow fermentation and potential undesirable flavors in the production of naturally fermented red wine. It not only shortens the production cycle and reduces production costs, but also highlights the terroir of the grape-growing region, significantly improving the quality of the wine. Furthermore, through physicochemical property analysis and sensory evaluation, the sensory quality of the naturally fermented red wine produced by this invention has been significantly improved, enhancing its style and quality. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0033] Figure 1 This is a flowchart of the brewing process according to an embodiment of the present invention;

[0034] Figure 2 The graphs show the trend of specific gravity changes during the fermentation process of wine in Examples 1-2 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0035] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0036] Example 1

[0037] like Figure 1 This invention provides a process for brewing naturally fermented red wine, specifically including the following steps:

[0038] (1) Preparation of mash enriched by natural microorganisms:

[0039] Raw material harvesting and sorting: Before harvesting, the ripeness of Cabernet Sauvignon grapes is tested to determine the ripe harvest period. Fresh grapes without disease, rotten fruit, mold, or green fruit are selected to obtain the best Cabernet Sauvignon grape raw materials.

[0040] Destemming, crushing and pulping: The Cabernet Sauvignon grapes are destemmed, crushed and pulped, and the process is completed quickly. The temperature of the resulting grape must is then lowered to 6°C.

[0041] Oxygenation in the tank: Transfer the grape must to the culture tank. During the oxygenation process, control the temperature of the grape must at 6°C and the oxygenation rate at 9 mg / L.

[0042] Multi-level gradient enrichment culture: After being placed in the tank, the grape must was heated to 12°C and subjected to multi-level gradient enrichment culture. The grape must was cultured at 12°C for 24 hours, then at 18°C ​​for 24 hours, and then at 24°C for 24 hours.

[0043] Separation and pressing: The enriched grape must is separated and pressed to obtain free-flowing must, and the pulp is pressed to obtain pressed must. The two are mixed to obtain mixed must. The mixed must is cooled to 2°C and stored for later use to obtain natural microbial enriched must.

[0044] (2) The production of naturally fermented red wine:

[0045] Raw material harvesting and sorting: Select ripe, fresh Cabernet Sauvignon grapes that are free from disease, rot, mold, and green fruit to obtain the best grape raw materials;

[0046] Destemming, crushing and pulping: The Cabernet Sauvignon grape raw materials are destemmed and crushed, then pulped. The process is completed quickly, and the temperature of the fermented grape must obtained after pulping is controlled at 18℃.

[0047] Inoculation into fermentation tank: Transfer the above grape must liquid into a fermentation tank. After inoculation, the natural microbial enriched must liquid obtained after inoculation is inoculated at 3% of the volume of the grape must liquid in the fermentation tank.

[0048] Alcoholic fermentation: The temperature is raised to 24℃ during natural fermentation, and then the fermentation temperature is controlled at 24℃. The specific gravity and temperature of the grape must are measured every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness and the alcoholic fermentation is ended. The fermentation time is about 12 days. The skins and pomace are separated to obtain the naturally fermented red grape wine.

[0049] Malolactic fermentation: The obtained naturally fermented red grape wine is temperature controlled at 22℃ to initiate malolactic fermentation naturally. When no malic acid is detected by paper chromatography, the malolactic fermentation is considered to be complete, and the naturally fermented Cabernet Sauvignon red wine is obtained.

[0050] Example 2

[0051] like Figure 1 This invention provides a process for brewing naturally fermented red wine, specifically including the following steps:

[0052] (1) Preparation of mash enriched by natural microorganisms:

[0053] Raw material harvesting and sorting: Before harvesting, the ripeness of Marselan grapes is tested to determine the ripe harvest period. Fresh grapes without disease, rotten fruit, mold, or green fruit are selected to obtain superior Marselan grape raw materials.

[0054] Destemming, crushing and pulping: The Marselan grape raw material is destemmed, crushed and pulped, and the process is completed quickly. The temperature of the grape must obtained after pulping is then lowered to 5°C.

[0055] Oxygenation in the tank: Transfer the grape must into the culture tank. During the oxygenation process, control the temperature of the grape must at 5°C and the oxygenation rate at 8 mg / L.

[0056] Multi-level gradient enrichment culture: After being placed in the tank, the grape must was heated to 14°C and subjected to multi-level gradient enrichment culture. The grape must was cultured at 14°C for 30 hours, then at 20°C for 30 hours, and then at 26°C for 30 hours.

[0057] Separation and pressing: The enriched grape must is separated and pressed to obtain free-flowing must, and the pulp is pressed to obtain pressed must. The two are mixed to obtain mixed must. The mixed must is cooled to 1°C and stored for later use to obtain natural microbial enriched must.

[0058] (2) The production of naturally fermented red wine:

[0059] Raw material harvesting and sorting: Select ripe, fresh Marselan grapes that are free from disease, rot, mold, and green fruit to obtain superior grape raw materials;

[0060] Destemming, crushing and pulping: The Cabernet Sauvignon grape raw materials are destemmed and crushed, then pulped. The process is completed quickly, and the temperature of the fermented grape must obtained after pulping is controlled at 16℃.

[0061] Inoculation into fermentation tank: Transfer the above grape must liquid into a fermentation tank. After inoculation into the tank, the natural microbial enriched must liquid obtained is inoculated at 4% of the volume of the grape must liquid in the fermentation tank.

[0062] Alcoholic fermentation: The temperature is raised to 25℃ during natural fermentation, and then the fermentation temperature is controlled at 25℃. The specific gravity and temperature of the grape must are measured every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness and the alcoholic fermentation is ended. The fermentation time is about 12 days. The skins and pomace are separated to obtain the naturally fermented red grape wine.

[0063] Malolactic fermentation: The obtained naturally fermented red grape wine is temperature controlled at 24℃ to initiate malolactic fermentation naturally. When no malic acid is detected by paper chromatography, the malolactic fermentation is considered to be complete, and the naturally fermented Cabernet Sauvignon red wine is obtained.

[0064] Comparative Example 1

[0065] A winemaking process for naturally fermented red wine is provided, specifically including the following steps:

[0066] Before harvesting the raw materials, the ripeness of Cabernet Sauvignon grapes is tested to determine the ripeness and harvest period. Fresh grapes without disease, rotten fruit, mold, or green fruit are selected to obtain the best Cabernet Sauvignon grape raw materials.

[0067] Destemming, crushing and pulping: The Cabernet Sauvignon grapes are destemmed, crushed and pulped. The process is completed quickly, and the temperature of the resulting grape must is controlled at 18℃.

[0068] Transfer to fermentation tank: Transfer the above grape must liquid into a fermentation tank;

[0069] Alcoholic fermentation: The temperature is raised to 24℃ during natural fermentation, and then the fermentation temperature is controlled at 24℃. The specific gravity and temperature of the grape must are measured every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness and the alcoholic fermentation is ended. The fermentation time is about 16 days. The skins and pomace are separated to obtain the naturally fermented red grape wine.

[0070] Malolactic fermentation: The obtained naturally fermented red grape wine is temperature controlled at 22℃ to initiate malolactic fermentation naturally. When no malic acid is detected by paper chromatography, the malolactic fermentation is considered to be complete, and the naturally fermented Cabernet Sauvignon red wine is obtained.

[0071] Comparative Example 2

[0072] A winemaking process for naturally fermented red wine is provided, specifically including the following steps:

[0073] Before harvesting the raw materials, the ripeness of Marselan grapes is tested to determine the ripeness and harvest period. Fresh grapes without disease, rotten fruit, mold, or green fruit are selected to obtain the best Marselan grape raw materials.

[0074] Destemming, crushing and pulping: The Marselan grape raw material is destemmed, crushed and pulped. The process is completed quickly, and the temperature of the grape must obtained after pulping is controlled at 16℃.

[0075] Transfer to fermentation tank: Transfer the above grape must liquid into a fermentation tank;

[0076] Alcoholic fermentation: The temperature is raised to 25℃ during natural fermentation, and then the fermentation temperature is controlled at 25℃. The specific gravity and temperature of the grape must are measured every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness and the alcoholic fermentation is ended. The fermentation time is about 16 days. The skins and pomace are separated to obtain the naturally fermented red grape wine.

[0077] Malolactic fermentation: The obtained naturally fermented red grape wine is temperature controlled at 24℃ to initiate malolactic fermentation naturally. When no malic acid is detected by paper chromatography, the malolactic fermentation is considered to be complete, and the naturally fermented Marselan red wine is obtained.

[0078] Comparative Example 3

[0079] The difference from Example 1 is that a one-stage enrichment culture is used: after being placed in the tank, the grape must is heated to 24°C and cultured at 24°C for 72 hours; the remaining steps and parameters are the same as in Example 1.

[0080] Comparative Example 4

[0081] The difference from Example 2 is that a one-stage enrichment culture is used: after being placed in the tank, the grape must is heated to 26°C and cultured at 26°C for 90 hours; the remaining steps and parameters are the same as in Example 2.

[0082] The specific gravity parameters of the wine fermentation process in Examples 1 and 2 and Comparative Examples 1 and 2 were monitored, and the results are as follows: Figure 2 As shown, wine fermentation is a biochemical reaction process in which grape juice produces alcohol under the action of yeast. During this process, the sugar content of the fermentation liquid decreases and the alcohol concentration increases. Because the sugar concentration decreases and the alcohol concentration increases during wine alcoholic fermentation, the specific gravity (density) of the fermentation liquid changes. Therefore, the fermentation speed can be accurately and intuitively measured by the change in specific gravity. Figure 2 The changes in specific gravity during wine fermentation show that the naturally fermented red wines produced in Examples 1 and 2 fermented 4-5 days faster than those in Comparative Examples 1 and 2. Furthermore, both Examples 1 and 2 were able to fully complete alcoholic fermentation, while the naturally fermented red wine in Comparative Example 1 had a slightly higher specific gravity. This may be due to the high sugar content of the grapes, meaning that the natural fermentation of grapes with a high potential ethanol volume fraction may not be complete. In addition, a prolonged fermentation period can have adverse effects on the wine, such as undesirable flavors from harmful microorganisms, affecting wine quality. Therefore, Examples 1 and 1 demonstrate that the brewing method of this invention can, to a certain extent, increase the fermentation speed and promote the completion of alcoholic fermentation of high-sugar grapes.

[0083] The physicochemical properties of the wines in Examples 1 and 2 and Comparative Examples 1 and 2 were tested and analyzed. The test results are shown in Table 1. The alcohol content, total sugar, pH value, total acid and volatile acid were tested according to the methods specified in GB / T15038-2006 General Analytical Methods for Wines and Fruit Wines.

[0084] Table 1 Physicochemical parameters of wine

[0085]

[0086] Alcohol content and total sugar content, as the most basic physicochemical indicators of wine, contribute to its smooth and rounded character and are used to evaluate the completeness of alcoholic fermentation. According to the data in Table 1, the alcohol content of Example 1 is higher than that of Comparative Example 1, while the total sugar content of Comparative Example 1 is higher than that of Example 1. This is consistent with the above-mentioned proportions, indicating that Comparative Example 1 did not complete alcoholic fermentation. Grapes with a high potential ethanol volume fraction (i.e., high-sugar grapes) and using wild yeast during natural fermentation raise concerns about the completeness of alcoholic fermentation. The brewing method of this invention, to a certain extent, promotes the completion of alcoholic fermentation in high-sugar grapes.

[0087] Furthermore, the proportions of total acidity and volatile acidity in the comparative example are higher than those in the example. A small amount of acetic acid can enrich the taste of wine, but excessive amounts can produce unpleasant odors, resulting in poor flavor and reduced sensory quality. The ideal acetic acid content in wine is 0.1-0.3 g / L. Natural fermentation carries the risk of spoilage, and the activity of non-wine yeasts, lactic acid bacteria, acetic acid bacteria, and other microorganisms can all contribute to increased volatile acid content. The brewing method of this invention reduces the volatile acidity of naturally fermented red wine to a certain extent, possibly due to the inoculation of naturally enriched microbial grape must, which increases the number of beneficial, dominant, and distinctive fermentation microbial populations. This not only increases the fermentation speed but also avoids the negative impacts of undesirable microorganisms, thus improving the quality of naturally fermented red wine.

[0088] Sensory evaluations were conducted on the wines in Examples 1 and 2 and Comparative Examples 1 and 2. The sensory evaluation criteria are shown in Table 2, and the results are shown in Table 3.

[0089] Table 2 Sensory Evaluation Criteria

[0090]

[0091] Table 3. Sensory Evaluation Table for Wine

[0092]

[0093]

[0094] As shown in Table 2, the scores of the naturally fermented red wines obtained in Examples 1 and 2 are higher than those of the corresponding Comparative Examples 1 and 2, respectively. In particular, the score of the naturally fermented Cabernet Sauvignon red wine obtained in Example 1 is significantly higher than that of Comparative Example 1. This indicates that the sensory quality of the naturally fermented red wine obtained by the present invention is superior to that of naturally fermented red wine obtained by conventional brewing processes, and has reached a better level.

[0095] Microbial counts were performed on the first stage mash (24 h for Example 1 and Comparative Example 3, 30 h for Example 2 and Comparative Example 4), the second stage mash (48 h for Example 1 and Comparative Example 3, 60 h for Example 2 and Comparative Example 4), and the third stage mash (72 h for Example 1 and Comparative Example 3, 90 h for Example 2 and Comparative Example 4) of the enrichment culture in the preparation of naturally enriched mash in Examples 1, 2, and Comparative Examples 3 and 4.

[0096] The bacteria and yeast counts of the above four mash samples were performed according to the method in SN / T 4675.28-2016 "Counting of Bacteria, Molds and Yeasts in Exported Wines", and the results are shown in Table 3.

[0097] Table 3 Results of bacterial and yeast counts in grape must.

[0098]

[0099] The results in the table above show that, in all stages, the number of bacteria and yeast in the mash of Comparative Examples 3 and 4 was higher than that of their corresponding Examples 1 and 2. The number of yeast in the mash in the third stage consistently reached 10. 7 -10 8 The quantity is on the order of magnitude, which can meet the requirements for inoculation of grape must in the later stage. However, in terms of the number of bacteria, the ratio is 2-4 times that of the example, which can easily lead to a surge in the number of bacteria inoculated, affecting the quality of wine fermentation.

[0100] Furthermore, the results also showed that the increase in bacterial count was significantly greater than in the previous example over time, indicating that the single-stage enrichment culture significantly promoted bacterial reproduction. This is mainly because the single-stage enrichment culture directly used a higher culture temperature, while the multi-stage gradient enrichment culture used a gradual temperature increase. During this process, yeast gradually became dominant, inhibiting bacterial reproduction and reducing bacterial growth. This demonstrates that if high-temperature culture is directly introduced, although the yeast count increases, it also easily promotes bacterial reproduction, leading to an increase in the bacterial proportion. Based on the above results, compared to the single-stage enrichment culture, the multi-stage gradient enrichment culture used in the example not only meets the inoculation requirements of dominant yeasts for wine fermentation but also significantly inhibits bacterial reproduction, indirectly reducing the growth of harmful microorganisms and increasing the proportion of dominant, beneficial, and characteristic microorganisms in the naturally enriched mash.

[0101] Therefore, the brewing process of this invention can, on the one hand, increase the fermentation speed, shorten the fermentation time, improve production efficiency, and reduce certain production costs; on the other hand, it uses a multi-level gradient enrichment culture method to enrich the natural microorganisms on the surface of red wine grapes, and then inoculates them for the fermentation of naturally fermented red wine. This allows for the inoculation of more dominant, beneficial, and distinctive natural microbial populations in the initial stage of fermentation, which improves the sensory quality of the wine, helps to strengthen the "terroir" characteristics of the wine, and highlights the style of the wine given by the natural characteristic microorganisms of the grape-producing region.

[0102] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing microbially enriched mash to improve the fermentation speed and sensory quality of naturally fermented red wine, characterized in that, The specific steps include the following: (1) Grape must is obtained by destemming, crushing and pulping mature wine grapes; (2) The grape must is oxygenated, and after oxygenation, it is subjected to multi-level gradient enrichment culture. Then, the grape must after culture is separated to obtain free-flowing must and pomace. The pomace is pressed to obtain pressed must. The pressed must and the free-flowing must are mixed to obtain microbial enriched must. The multi-level gradient enrichment culture method is as follows: after culturing the grape must at 12-14℃ for 18-30h, the temperature is raised to 18-20℃ for 18-30h, and finally the temperature is raised to 24-26℃ for 18-30h. The oxygenation amount in step (2) is 8-10 mg / L, and the temperature of the oxygenated grape must is <7℃.

2. The method for preparing microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine according to claim 1, characterized in that, The wine grapes used in step (1) are fresh, disease-free, rotten, moldy, and unripe red varieties.

3. The method for preparing microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine according to claim 2, characterized in that, The red grape varieties used for winemaking are any one of Cabernet Sauvignon, Merlot, Pinot Noir, Marselan, Cabernet Gernischt, and Syrah.

4. A microbial enriched mash for improving the fermentation speed and sensory quality of naturally fermented red wine, obtained by the preparation method according to any one of claims 1-3.

5. The application of the microbial enriched mash as described in claim 4 in the brewing of naturally fermented red wine.

6. The application according to claim 5, characterized in that, The brewing process is as follows: 1) After destemming, crushing, and pulping ripe wine grapes, fermented grape must is obtained; 2) After inoculating the fermented grape must with the microbial enrichment, the wine is then subjected to alcoholic fermentation and malolactic fermentation in sequence to obtain naturally fermented red wine.

7. The application according to claim 6, characterized in that, The wine grapes mentioned in step 1) are fresh, disease-free, rotten, moldy, and unripe grapes of the same variety as the raw materials for microbial enrichment of the must.

8. The application according to claim 6, characterized in that, The inoculum amount of the microbial enrichment mash in step 2) is 2-4 wt%.

9. The application according to claim 6, characterized in that, The specific steps of alcoholic fermentation described in step 2) are as follows: natural fermentation is carried out at 24-26℃, and the specific gravity and temperature of the fermented grape must are measured every day. When the specific gravity drops to 0.992-0.996, the residual sugar is tested. When the residual sugar is below 4g / L, it indicates that the fermentation has reached dryness, and the alcoholic fermentation is ended. The skins and pomace are separated to obtain naturally fermented red grape wine. The specific steps of the malolactic fermentation are as follows: the naturally fermented red grape wine is naturally fermented at 22-24℃. When no malic acid is detected by malic acid paper chromatography, the malolactic fermentation is considered to be over, and the naturally fermented red wine is obtained.

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