Natural sweet wine low-sulfur brewing method for harvesting white grapes after white grapes turn red

Abstract

The invention belongs to the technical field of wine brewing, relates to a natural sweet wine low-sulfur brewing method for delaying white grapes until the white grapes turn red and then harvesting the white grapes, solves the health hidden danger and flavor defects caused by high-sulfur addition in the traditional sweet white wine process, and remarkably improves the flavor quality of the wine at the same time. According to the method, complete and healthy red (total anthocyanin content is greater than or equal to 5mg / kg) fruits are selected through artificial spike selection and grain selection, and the cardinal number of infectious microbes in raw materials is reduced; no commercial yeast is added, natural slow fermentation is achieved by means of microorganisms, and the finished product is good in flavor and quality; gallic acid, condensed tannin and hydrolyzed tannin with a ratio of 1: 1: 1 are compounded to prepare wine-brewing tannin, and the wine-brewing tannin and low-dose sulfur dioxide construct a synergistic system, so that the sulfur consumption of sulfur dioxide is greatly reduced, secondary fermentation of high-sugar wine liquid is prevented, and infectious microbes and wine body oxidation are effectively inhibited. The finished product biogenic amine, pesticide and heavy metal residues all meet the safety standard, mycotoxin is not detected, meanwhile, the original flavor of the wine body is prominent, the storage stability is good, and dual guarantee of health and quality is achieved.

Description

Technical Field

[0001] This invention belongs to the field of winemaking technology and relates to a low-sulfur winemaking method for naturally sweet wine made from white grapes that are harvested after they have turned red. Background Technology

[0002] Sweet white wine is an important category in the high-end wine market. The core logic is to retain the natural sugar content of grapes and maximize the presentation of the raw material flavor. With the upgrading of consumption, the market demand for its natural attributes, health and safety and unique terroir expression is becoming increasingly prominent.

[0003] Sweet white wines can be clearly divided into two categories: one is raw material-dependent, naturally high-sugar products, such as ice wine which requires late harvesting and low-temperature freezing and pressing; botrytized wine which requires late harvesting and relies on Botrytis cinerea (noble rot) infection to achieve flavor transformation; and conventional late-harvest wine which concentrates sugar through natural dehydration by delaying harvesting. These methods often involve fermenting all late-harvest fruits together, ignoring the reddening and wrinkling characteristics of some fruits induced by special climate during the late-harvest stage and their unique flavor value. Although these three types can present a naturally high-sugar flavor, they are extremely dependent on the environment, and botrytized wine is prone to fruit spoilage. The other category is process-intervention products, which achieve sweetness through artificial fermentation, high-sulfur addition + sugar supplementation, reverse osmosis and other concentration processes, lacking naturalness and flavor complexity.

[0004] Late-harvested raw materials face the problem of "complex microorganisms and difficulty in initiating natural fermentation." Existing processes can only add high sulfur to suppress miscellaneous bacteria, which not only raises the risk of allergies but also damages the flavor of the raw materials. Especially during the rainy harvest season, the predicament of both types of products is exacerbated. Raw material-dependent products are prone to mold growth due to poor moisture resistance of the varieties, making it impossible to delay harvesting. Process-intervention-dependent products suffer further flavor degradation due to the decline in raw material quality.

[0005] Therefore, developing a sweet white wine production process that uses late-harvested red grapes as raw materials, is low in sulfur and healthy, and is suitable for rainy environments, in order to make up for the limitations of existing technologies in terms of raw materials and health benefits, has become an urgent need for the industry. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a low-sulfur winemaking method for naturally sweet wine made from white grapes harvested after they have turned red, specifically comprising the following steps:

[0007] Step 1: Select healthy white grapes with a reddish appearance (total anthocyanin content in fresh skin ≥5mg / kg), a wrinkling rate ≥15%, a breakage rate ≤3%, reducing sugar ≥290g / L, total acid 6-8g / L, and pH 3.3-3.4. In an anaerobic environment, press the selected white grapes at 0.1-0.2 bar for 20-30 minutes and at 0.3-0.5 bar for 40-60 minutes, yielding a juice yield of 55-60%.

[0008] Preferably, the white grapes are selected from thick-skinned varieties that are prone to turning red and are highly resistant to moisture. These varieties are less prone to mold growth in rainy environments and can naturally concentrate sugar and flavor substances after turning red, making them more suitable for making low-sulfur red sweet white wines. Therefore, one or more of Petit Mansson, Viognier and Vidal are selected.

[0009] Step two: No commercial yeast is added in this step. The grape juice is poured into a fermentation tank, filling it to 3 / 4 of its volume. The free SO2 concentration is adjusted to 25-30 mg / L. 30-35 mg / L of pectinase, 45-50 mg / L of winemaking tannins, and 1500-1600 mg / L of organic acids are added. SO2 acts as a sterilizer and antioxidant. Pectinase promotes the decomposition of pectin in the grape juice, improving its clarity and filtration efficiency. Grape tannins enhance the structure and antioxidant capacity of the wine, working synergistically with SO2 to reduce oxidation risks. Organic acids maintain the wine's sweet and sour balance, enhancing the drinking experience.

[0010] Fermentation is then carried out at 12-18℃. This temperature range is conducive to the activation and reproduction of the native microbial community on the grape surface, promoting the smooth start of fermentation. This process does not add any commercial yeast, relying on the natural microbial community to complete the fermentation. After 9-10 days, the temperature is adjusted to 11-15℃, and the specific gravity is monitored daily to ensure that the residual sugar content is higher than 90g / L and the specific gravity decreases by 0.003-0.004 per day. After 130-135 days or when the specific gravity is 1.026-1.028, potassium metabisulfite is added to adjust the free sulfur concentration to 20-25mg / L to obtain the original wine liquid.

[0011] Preferably, the organic acid is one or more selected from citric acid, malic acid, and tartaric acid. Most preferably, the organic acid is tartaric acid.

[0012] Preferably, the brewing tannins include gallic acid, condensed tannins and hydrolyzed tannins in a mass ratio of 1:1:1.

[0013] Step 3: Add 410-520 mg / L of compound clarifying agent to the original wine liquid, let it stand at 4-5℃ for 7-14 days, add 5-6 mg / L of winemaking tannins to further enhance the structure and antioxidant capacity of the wine, improve the quality and aging potential of the wine, add potassium metabisulfite to adjust the free sulfur concentration to 25-30 mg / L, filter through a 0.45μm filter membrane to remove larger particulate impurities and some microorganisms, and then filter through a 0.22μm filter membrane to remove most microorganisms and fine impurities. Use champagne bottles + crown caps to bottling and seal in an aseptic environment. Champagne bottles resist the pressure of the high sugar body of the wine, and crown caps isolate oxygen. Store at 0-4℃, 60-70%RH, and away from light. Monitor the physicochemical indicators such as residual sugar, acidity, and microorganisms every 3 months.

[0014] Preferably, the composite clarifying agent comprises 400-500 mg / L of bentonite and 10-20 mg / L of polyvinylpyrrolidone.

[0015] The present invention has the following advantages:

[0016] (1) The fermentation process of this invention differs from traditional brewing techniques. It uses specially formulated brewing tannins and trace amounts of SO2 to construct a synergistic system, which can inhibit the growth of miscellaneous bacteria, create an advantageous environment for the growth of native yeasts, solve the problem of difficulty in starting natural fermentation of late-harvested raw materials, and reduce the amount of SO2 used, thereby reducing health risks. The low-temperature fermentation environment further inhibits the activity of miscellaneous bacteria, reduces the production of undesirable metabolites, and at the same time prolongs the fermentation cycle, promoting the full dissolution and transformation of unique flavor substances such as anthocyanins and flavonoids in the ripening fruit, thus enhancing the complexity of the wine's flavor.

[0017] (2) This invention achieves the optimal selection and standardization of raw materials through an innovative scheme of "precise selection of ripening berries and matching of raw materials." Unlike traditional late-harvest wines that mix ripening and non-ripening berries, this method combines manual bunch selection and manual berry selection to precisely screen healthy berries with ripening appearance (total anthocyanin content ≥5mg / kg in fresh skin), wrinkling rate ≥15%, reducing sugar ≥290g / L, total acid 6-8g / L, and pH 3.3-3.4, while removing non-ripening, moldy, and damaged berries. This screening system not only ensures the uniformity and high purity of the raw materials but also focuses on the unique flavor compounds of ripening berries (such as anthocyanins and flavonoids), providing a high-quality raw material guarantee for subsequent winemaking. Simultaneously, this method prioritizes thick-skinned white grape varieties with strong moisture resistance and easy ripening, enhancing the adaptability of the raw materials in rainy environments and improving the product's unique flavor and winemaking stability from the source.

[0018] (3) This invention utilizes a "low-temperature, long-term natural fermentation" process to fully stimulate and transform the flavor potential of the raw materials. Based on carefully selected grapes ripening to red, a natural fermentation method without the addition of commercial yeast is adopted. Relying on the local microbial community on the surface of the grapes, fermentation is initiated at 12-18℃, followed by slow fermentation at 11-15℃ for more than 130 days. This process inhibits the growth of unwanted bacteria and reduces harmful metabolites by lowering the temperature. On the other hand, it extends the fermentation period, promoting the full dissolution, transformation, and fusion of unique flavor substances such as anthocyanins and flavonoids in the ripening grapes. At the same time, a precise acid-adjusting process balances the sweetness and acidity of the wine, resulting in a richer flavor profile and a more harmonious taste. This fully showcases the unique terroir of late-harvest ripening grapes and solves the problem of monotonous flavor in traditional processes.

[0019] (4) This invention leverages the unique raw material advantage of "late-harvest red wine" and combines the complex aromas from natural fermentation with the health benefits of low-sulfur processing to create a high-end sweet white wine that is natural, unique, and safe. The product achieves high sweetness without the need for sugar supplementation, avoiding the flavor dilution problem caused by artificial sugar supplementation. It is significantly differentiated from traditional sweet white wines, perfectly meeting the current market's personalized and health-conscious consumer demands, and significantly enhancing its market competitiveness. Attached Figure Description

[0020] 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. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 Radar chart showing the sensory characteristics of wine samples from Examples 1-3 and the control group. Detailed Implementation

[0022] The technical solutions in the embodiments of the invention are described clearly and completely below. 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.

[0023] The following is a formulation of brewing tannins: the brewing tannins include gallic acid, condensed tannins and hydrolyzed tannins, in a mass ratio of 1:1:1.

[0024] Example 1

[0025] Step 1: Select disease-free Little Mansé grapes with a total anthocyanin content ≥5mg / kg, a wrinkling rate of 18%, a breakage rate of 2%, a reducing sugar content of 295g / L, a total acid content of 6.8g / L, and a pH of 3.32. Under carbon dioxide protection, press the selected white grapes at 0.15 bar for 25 minutes and then at 0.4 bar for 50 minutes, yielding a juice yield of 58%.

[0026] Step two: The grape juice is poured into a fermentation tank, filling it to 3 / 4 of its volume. The free SO2 concentration is adjusted to 30 mg / L. 30 mg / L pectinase, 50 g / t winemaking tannins, and 1.5 kg / t tartaric acid are added. Fermentation is carried out at 15°C for 9 days, then the temperature is adjusted to 13°C. The specific gravity is monitored daily to ensure a daily decrease of 0.0035. After 130 days, when the specific gravity is 1.028 and the residual sugar content is 92 g / L, potassium metabisulfite is added to adjust the free sulfur concentration to 20 mg / L, yielding the original wine liquor.

[0027] Step 3: Add 450g / t of bentonite and 15g / t of PVPP to the original wine liquid, let it stand at 4℃ for 7 days, add 5g / t of winemaking tannin and potassium metabisulfite to adjust the free sulfur concentration to 28mg / L, filter through a 0.45μm filter membrane and then through a 0.22μm filter membrane, and store at 2℃, 65%RH, away from light.

[0028] Example 2

[0029] The difference from Example 1 is as follows: Step 1: Vioni variety was selected, with reducing sugar 292 g / L, total acid 6.5 g / L, pH 3.30, shrinkage rate 16%, and breakage rate 1.5%. Step 2: Citric acid was used, fermentation was carried out at 12℃ for 9 days, the temperature was adjusted to 11℃, pressing was performed at 0.1 bar for 20 min, and at 0.3 bar for 40 min, with a juice yield of 55%. Fermentation was carried out at 13℃ for 9 days, the temperature was adjusted to 12℃, ensuring that the specific gravity decreased by 0.003 per day. After 130 days, the specific gravity was 1.027, and the residual sugar content was 95 g / L. Step 3: 400 g / t of bentonite and 10 g / t of PVPP were added to adjust the free sulfur concentration to 25 mg / L, and the product was stored at 0℃, 60% RH, and protected from light.

[0030] Example 3

[0031] The difference from Example 1 is as follows: Step 1: Vidal grape variety was selected, with reducing sugar 298 g / L, total acid 7.2 g / L, pH 3.35, shrinkage rate 20%, and breakage rate 2.5%. Step 2: Citric acid was used, fermentation was carried out at 18℃ for 9 days, the temperature was adjusted to 15℃, pressing was performed at 0.2 bar for 30 min, and at 0.5 bar for 60 min, with a juice yield of 60%. Fermentation was carried out at 17℃ for 9 days, the temperature was adjusted to 14℃, ensuring that the specific gravity decreased by 0.004 per day. After 130 days, the specific gravity was 1.029, and the residual sugar content was 93 g / L. Step 3: 500 g / t bentonite and 20 g / t PVPP were added to adjust the free sulfur concentration to 30 mg / L, and the product was stored at 4℃, 70% RH, and protected from light.

[0032] Experimental Example 1

[0033] The white grape-to-red sweet white wines produced using the methods in Examples 1-3 have a clear and bright appearance, complex and rich fruit and wine aromas, a mellow and harmonious taste, and no off-flavors, exhibiting typical wine characteristics. Their physicochemical indicators fully comply with the requirements of the new national standard for wine, GB15037-2006. The main flavor compounds, biogenic amines, pesticide residues, and heavy metal content in the sweet white wine of Example 1 were identified, and the results are shown in Tables 1-4.

[0034] Table 1. Volatile substance content of wine sample in Example 1

[0035] Serial Number Substance Name CAS number Content (mg / L) 1 Ethyl acetate 141-78-6 122.29±0.99 2 2,3-Butanedione 431-03-8 1.29±0.01 3 Isobutyl acetate 110-19-0 0.03±0.002 4 Ethyl butyrate 105-54-4 0.45±0.005 5 ethyl 2-methylbutyrate 624-41-9 0.0032±0.0000 6 Ethyl isobutyrate 97-62-1 10.16±0.10 7 Isobutanol 78-83-1 44.57±0.48 8 Isoamyl acetate 123-92-2 21.43±0.20 9 n-Butanol 71-36-3 1.56±0.02 10 Isoamyl alcohol 123-51-3 305.02±3.40 11 Ethyl hexanoate 123-66-0 4.95±0.05 12 3-Methyl-1-pentanol 589-35-5 0.03±0.0003 13 Ethyl lactate 97-64-3 0.10±0.001 14 Hexanol 111-27-3 1.47±0.02 15 (E)-3-hexen-1-ol 928-96-1 0.02±0.0002 16 Methyl octanoate 111-11-5 0.01±0.0001 17 (E)-2-hexen-1-ol 928-95-0 1.04±0.01 18 Ethyl octanoate 106-32-1 17.53±0.20 19 1-Octen-3-ol 3391-86-4 0.02±0.0002 20 Acetic acid 64-19-7 690.59±7.54 21 Isoamyl hexanoate 2173-56-0 0.02±0.0001 22 Ethyl nonanoate 123-29-5 0.03±0.0004 23 Aromatic alcohols 78-70-6 0.02±0.0003 24 Octal 124-13-0 0.22±0.003 25 Isobutyric acid 79-31-2 2.76±0.03 26 2,3-Butanediol 513-85-9 1303.15±13.00 27 4-Terpineol 565-48-0 0.02±0.0003 28 Ethyl decanoate 110-38-3 7.79±0.09 29 phenylacetaldehyde 122-78-1 0.06±0.0006 30 Isovalerate 503-74-2 0.30±0.003 31 Diethyl succinate 123-25-1 0.46±0.005 32 alpha-terpineol 98-55-5 0.01±0.0001 33 3-Methylthiopropanol 505-10-2 1.60±0.02 34 Citronellol 106-22-9 0.01±0.0001 35 Geraniol acetate 105-87-3 0.02±0.0002 36 Phenylacetyl acetate 103-45-7 0.16±0.002 37 beta-damascone 23696-85-7 0.01±0.0001 38 Ethyl lauryl acid 106-33-2 2.33±0.02 39 Phenylacetyl alcohol 22258 47.05±0.51 40 β-ionone 14901-07-6 0.0003±0.0000 41 phenol 108-95-2 0.04±0.0005 42 bitter 124-07-2 1.36±0.02 43 Ethyl palmitate 628-97-7 0.16±0.002 44 Decanoic acid 334-48-5 0.62±0.01

[0036] Table 2. Content of non-volatile phenolic substances in wine sample from Example 1

[0037] Serial Number Substance Name m / z value CAS Content (mg / L) 1 gallic acid 169.0149 149-91-7 7.28±0.04 2 p-hydroxybenzoic acid 137.0242 99-96-7 0.41±0.03 3 Protocatechuic acid 153.0196 99-50-3 1.14±0.06 4 clove acid 197.0454 530-57-4 3.23±0.22 5 caffeic acid 179.0356 331-39-5 79.30±4.08 6 p-coumaric acid 163.0401 501-98-4 1.22±0.09 7 ferulic acid 193.0506 1135-24-6 1.45±0.03 8 vanillic acid 167.0349 121-34-6 4.22±0.09 9 trans-resveratrol 227.0722 501-36-0 2.15±0.06 10 Rutin 609.1469 153-18-4 0.11±0.02 11 Quercetin 301.0362 117-39-5 0.02±0.002 12 Kaempferol 285.0413 520-18-3 0.01±0.002 13 Gallo-tea element 305.0675 3371-27-5 0.67±0.03 14 Epigallocatechin 305.0675 970-74-1 2.68±0.06 15 Catechins 289.0724 154-23-4 0.23±0.01 16 Catechin 289.0726 490-46-0 0.68±0.17 17 Proanthocyanidins B4 577.1354 29106-49-8 0.09±0.001 18 Proanthocyanidins B3 577.1354 23567-23-9 0.02±0.002 19 Proanthocyanidins B1 577.1357 20315-25-7 0.03±0.003

[0038] Table 3. Detection results of biogenic amines, mycotoxins, and ethyl carbamate in wine samples from Example 1.

[0039] Serial Number Testing items Test results unit Remark 1 histamine 95 µg / L Biogenic amines 2 Cadaniamine 42 µg / L Biogenic amines 3 putrescine 9800 µg / L Biogenic amines 4 Tyramine 17 µg / L Biogenic amines 5 2-Phenylacetamine 356 µg / L Biogenic amines 6 Ethyl carbamate Not detected mg / kg harmful substances 7 Ochratoxin A Not detected μg / kg Mycotoxins 8 Aflatoxin G1 Not detected μg / kg Mycotoxins 9 Aflatoxin B2 Not detected μg / kg Mycotoxins 10 Aflatoxin B1 Not detected μg / kg Mycotoxins 11 Aflatoxin G2 Not detected μg / kg Mycotoxins 12 Deoxynivalenol Not detected μg / kg Mycotoxins 13 Patulin Not detected μg / kg Mycotoxins 14 Zearalenone Not detected μg / kg Mycotoxins 15 Fumonisin B1 Not detected μg / kg Mycotoxins 16 Fumonisin B2 Not detected μg / kg Mycotoxins 17 Fumonisin B3 Not detected μg / kg Mycotoxins 18 Aspergillus violaceus Not detected μg / kg Mycotoxins 19 Aflatoxin M1 Not detected μg / kg Mycotoxins

[0040] Table 4. Detection results of pesticide and heavy metal residues in wine samples from Example 1

[0041] Serial Number Testing items Test results unit Remark 1 High-efficiency cyhalothrin Not detected mg / kg pesticide residues 2 Avermectin Not detected mg / kg pesticide residues 3 Pyraclostrobin Not detected μg / kg pesticide residues 4 Pyridaben Not detected mg / kg pesticide residues 5 difenoconazole Not detected mg / kg pesticide residues 6 Bifenthrin Not detected mg / kg pesticide residues 7 Emamectin benzoate Not detected μg / kg pesticide residues 8 Imidacloprid Not detected μg / kg pesticide residues 9 iprodione Not detected mg / kg pesticide residues 10 pyrimethanil Not detected mg / kg pesticide residues 11 Thiamethoxam Not detected μg / kg pesticide residues 12 Metalaxyl Not detected μg / kg pesticide residues 13 Dimethomorph 0.18 μg / kg pesticide residues 14 Carbendazim 3.8 μg / kg pesticide residues 15 glyphosate Not detected mg / kg pesticide residues 16 copper 0.068 mg / L heavy metal 17 lead Not detected mg / kg heavy metal

[0042] As shown in Tables 1-4, this product is rich in unique substances such as anthocyanins and flavonoids, with 44 volatile aroma components and 19 non-volatile phenolic compounds. Its aroma is more complex and unique, and its nutritional components are richer than those of traditional sweet white wines. The formation of these flavor compounds and nutrients is closely related to the characteristics of the ripening grapes and the winemaking process: the flavor precursors and phenolic compounds stored in the ripening grapes themselves form the foundation; low-temperature, long-term natural fermentation promotes the transformation and accumulation of flavor compounds; and the synergistic system of no added commercial yeast, low sulfur, and winemaking tannins maximizes the preservation of natural flavors and nutrients, avoiding the damage caused by artificial additives. The product's biogenic amine content meets safety standards, and pesticide residues and heavy metal content are far below the limits, making it safer to drink. The product achieves high sweetness without the need for added sugar, and its residual sugar is stable.

[0043] Experimental Example 2

[0044] The basic physicochemical indicators, color, main flavor compounds, biogenic amines, pesticide residues, and heavy metal content of the white grape-to-red sweet white wines prepared in Examples 1-3 above were identified. A sensory analysis was conducted by an expert team, and the results were compared with a control group (traditional sweet white wine). The results are shown in Tables 5-9. Figure 1 .

[0045] The control group's winemaking process is as follows: Step 1: Select mature, undamaged, ordinary late-harvest white grapes, press them as usual to extract the juice. Step 2: Transfer the grape juice to a fermentation tank, adjust the free SO2 to 95 mg / L, add commercial yeast, ferment at 18-20℃ until the target residual sugar is reached, add high sulfur to terminate fermentation, and obtain the original wine liquid. Step 3: Add bentonite and allow to stand for clarification, filter as usual, adjust the free sulfur to 100-150-120 mg / L, and store at room temperature away from light.

[0046] Table 5 Comparison of main physicochemical indicators between Examples 1-3 and the control group

[0047] project Example 1 Example 2 Example 3 control group Alcohol content (%vol) 12.65±0.18 12.52±0.21 12.70±0.15 12.30±0.25 Reducing sugar (g / L) 92.15±2.68 90.87±2.75 93.42±2.61 85.32±3.10 pH 3.31±0.02 3.29±0.03 3.33±0.02 3.45±0.04 Total acid (g / L) 7.38±0.09 7.43±0.07 7.35±0.10 6.85±0.12 Free sulfur (mg / L) 28.65±1.68 25.32±1.55 29.87±1.72 155.42±5.30 Total sulfur (mg / L) 115.86±4.42 114.35±4.60 117.52±4.38 320.58±6.25

[0048] Table 6 Comparison of color parameters of wine samples from Examples 1-3 and the control group

[0049] Wine sample L* a* b* C* H* control group 88.34 -1.4 14.1 14.17 -55.81 Example 1 94.29 -1.89 15.95 16.06 -1.45 Example 2 92.65 -1.75 15.4 15.52 -38.5 Example 3 90.78 -1.62 14.9 15 -46.2

[0050] Table 7 Comparison of volatile substance content between Examples 1-3 and the control group

[0051] Table 8. Content of non-volatile phenolic substances in wine samples from Examples 1-3 and the control group.

[0052] Substance Name Example 1 (mg / L) Example 2 (mg / L) Example 3 (mg / L) Control group (mg / L) gallic acid 7.28±0.04 6.85±0.04 7.12±0.04 5.32±0.03 p-hydroxybenzoic acid 0.41±0.03 0.38±0.02 0.40±0.03 0.29±0.02 Protocatechuic acid 1.14±0.06 1.06±0.05 1.11±0.06 0.82±0.04 clove acid 3.23±0.22 3.02±0.20 3.15±0.21 2.35±0.18 caffeic acid 79.30±4.08 74.25±3.85 77.18±3.98 58.65±3.20 p-coumaric acid 1.22±0.09 1.14±0.08 1.19±0.09 0.89±0.07 ferulic acid 1.45±0.03 1.36±0.03 1.42±0.03 1.05±0.02 vanillic acid 4.22±0.09 3.95±0.08 4.11±0.09 3.08±0.07 trans-resveratrol 2.15±0.06 2.01±0.05 2.10±0.06 1.58±0.04 Rutin 0.11±0.02 0.10±0.02 0.11±0.02 0.07±0.01 Quercetin 0.02±0.002 0.018±0.002 0.019±0.002 0.013±0.001 Kaempferol 0.01±0.002 0.009±0.002 0.0095±0.002 0.006±0.001 Gallo-tea element 0.67±0.03 0.62±0.03 0.65±0.03 0.48±0.02 Epigallocatechin 2.68±0.06 2.50±0.05 2.61±0.06 1.95±0.04 Catechins 0.23±0.01 0.21±0.01 0.22±0.01 0.16±0.01 Catechin 0.68±0.17 0.63±0.15 0.66±0.16 0.49±0.12 Proanthocyanidins B4 0.09±0.001 0.083±0.001 0.087±0.001 0.065±0.001 Proanthocyanidins B3 0.02±0.002 0.018±0.002 0.019±0.002 0.014±0.001 Proanthocyanidins B1 0.03±0.003 0.027±0.002 0.029±0.003 0.021±0.002

[0053] Table 9 Comparison of the detection results of biogenic amines, mycotoxins, and ethyl carbamate in wine samples from Examples 1-3 and the control group.

[0054] Testing items Example 1 Example 2 Example 3 control group unit histamine 95 90 92 125 µg / L Cadaniamine 42 38 40 55 µg / L putrescine 9800 9500 9650 11200 µg / L Tyramine 17 15 16 23 µg / L 2-Phenylethylamine 356 330 345 420 µg / L Ethyl carbamate Not detected Not detected Not detected 0.03±0.01 mg / kg Ochratoxin A Not detected Not detected Not detected Not detected μg / kg Aflatoxin G1 Not detected Not detected Not detected Not detected μg / kg Aflatoxin B2 Not detected Not detected Not detected Not detected μg / kg Aflatoxin B1 Not detected Not detected Not detected Not detected μg / kg Aflatoxin G2 Not detected Not detected Not detected Not detected μg / kg Deoxynivalenol Not detected Not detected Not detected 15±2 μg / kg Patulin Not detected Not detected Not detected 12±1 μg / kg Zearalenone Not detected Not detected Not detected 75±3 μg / kg Fumonisin B1 Not detected Not detected Not detected 18±2 μg / kg Fumonisin B2 Not detected Not detected Not detected 14±1 μg / kg Fumonisin B3 Not detected Not detected Not detected 12±1 μg / kg Aspergillus violaceus Not detected Not detected Not detected 3±0.5 μg / kg Aflatoxin M1 Not detected Not detected Not detected Not detected μg / kg

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-sulphur brewing method for white grape natural sweet wine with delayed harvest to post-red, characterized by, Includes the following steps: Step 1: Select healthy white grapes with a total anthocyanin content ≥5mg / kg, a wrinkling rate ≥15%, a breakage rate ≤3%, a reducing sugar content ≥290g / L, a total acid content of 6-8g / L, and a pH of 3.3-3.4 in the fresh skin. Press the grapes at 0.1-0.5 bar for 60-90 minutes in an anaerobic environment to obtain grape juice. Step two: In this step, no commercial yeast is added. The free SO2 in the grape juice is adjusted to 25-30 mg / L, and 30-35 mg / L pectinase, 45-50 mg / L winemaking tannins and 1500-1600 mg / L organic acids are added. Fermentation is carried out at 11-18℃ for 139-145 days or when the specific gravity is 1.026-1.

029. Potassium metabisulfite is added to adjust the free sulfur concentration to 20 mg / L to terminate fermentation, and the original wine liquid is obtained. Step 3: Add 410-520 mg / L of compound clarifying agent to the original wine liquid, let it stand at 4-5℃ for 7-14 days, add 5-6 mg / L of grape tannin and potassium metabisulfite, adjust the free sulfur concentration to 25-30 mg / L, filter through a 0.22-0.45 μm filter membrane, and store at 0-4℃ and 60-70% RH in the dark.

2. A low-sulphur natural sweet wine brewing method for white grape delayed harvest to red grape according to claim 1, characterized in that, In step one, press at 0.1-0.2 bar for 20-30 minutes, then press at 0.3-0.5 bar for 40-60 minutes.

3. A low sulphur natural sweet wine brewing method of white grape for delayed harvest to red after, according to claim 1, characterized in that, In step one, the white grape varieties are one or more of Petit Mansé, Viognier, and Vidal.

4. A low-sulphur natural sweet wine brewing method for white grape delayed to red after harvest according to claim 1, characterized in that, In step two, ferment at 12-18℃ for 9 days, then at 11-15℃ for 130 days. When the residual sugar content is higher than 90g / L, add potassium metabisulfite to stop fermentation.

5. A low-sulphur natural sweet wine brewing method for white grape delayed to red after harvest according to claim 1, characterized in that, In step three, after filtration, the wine is bottled and sealed in a champagne bottle with a crown cap in a sterile environment.

6. A low-sulphur natural sweet wine brewing method for white grape delayed to red after harvest according to claim 1, characterized in that, The brewing tannins mentioned in step two include gallic acid, condensed tannins and hydrolyzed tannins, in a mass ratio of 1:1:

1.

7. A low-sulphur natural sweet wine brewing method for white grape delayed to red after harvest according to claim 1, characterized in that, The organic acid mentioned in step two is one or more of citric acid, malic acid, and tartaric acid.

8. A low sulphur natural sweet wine brewing method of white grape delayed to harvest after veraison according to claim 1, characterized in that, The composite clarifying agent mentioned in step three includes 400-500 g / t of bentonite and 10-20 g / t of polyvinylpyrrolidone.

9. A low sulphur natural sweet wine brewing method of white grape for delayed harvest to red wine according to claim 1, characterized in that, In step three, the filter first passes through a 0.45μm filter membrane and then through a 0.22μm filter membrane.

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