Method for controlling content of ethyl carbamate in dry white wine

Abstract

The invention relates to the technical field of wine brewing, in particular to a method for controlling the content of ethyl carbamate in dry white wine, which comprises the following steps: planting grapes, determining a harvesting time, harvesting, selecting ears, removing stalks, selecting grains, crushing, cooling and taking juice, clarifying at low temperature, separating juice and returning temperature, fermenting at low temperature by alcohol, pouring into a tank, storing at low temperature and detecting. The method comprises the following steps: controlling the content of a key substrate urea to be at a low level, fining and clarifying, freezing, filtering, sterilizing, filling, inspecting physicochemical indexes, microbiological indexes and sensory evaluation of grape wine, filling after inspection and evaluation are qualified, and controlling the temperature to be within 20 DEG C. The method covers the whole grape wine brewing process of grape raw materials, raw wine fermentation, ageing and the like; the method is a systematic solution, and the increase of the ethyl carbamate in the dry white wine is effectively controlled.

Description

Technical Field

[0001] The invention relates to the technical field of winemaking, in particular to a method for controlling the content of ethyl carbamate in dry white wine. Background Art

[0002] Ethyl carbamate (EC) is a natural byproduct of the production and storage of most fermented foods (such as bread, milk, etc.) and alcoholic beverages (beer, liquor, wine, etc.). In 2007, the International Agency for Research on Cancer upgraded the carcinogenicity level of EC from the previous 2B to 2A, and some major wine producing countries have also successively established limits for EC in wine. The limit of EC in American table wine is 15μg·L -1 The EC limit in wines from Canada, South Korea and the Czech Republic is 30 μg·L -1 At present, my country has not yet formulated a limit standard for EC in wine. In recent years, as food safety has become increasingly important, EC, as a potential carcinogen, has gradually attracted social attention and has become a key safety control indicator. Existing studies have basically clarified the pathways and main influencing factors of EC in wine, but lack quantitative indicators of each influencing factor. At the same time, the generation of EC is closely related to the management of the entire production process, including grape planting, raw material quality, fermentation and aging. Compared with dry red wine, it is more difficult to control the EC content in dry white wine.

[0003] The Chinese invention patent application with publication number CN107189903A discloses a brewing scheme for ethyl carbamate fruit wine, wherein yeasts with strong urea metabolism levels can be screened out by culturing yeasts in a medium with high urea content, and yeast strains with strong urea tolerance and high metabolic capacity can be screened out by gradually increasing the urea content level, thereby reducing the urea content in fermentation and thus reducing the output of ethyl carbamate in fermentation; the ethyl carbamate component is obtained by adding acid urease to the fermentation substrate and the mixed fermentation filtrate before the first fermentation, thereby inhibiting and eliminating the production of urea in the fermentation, and the acid urease can decompose the urea component in the fermentation liquid, thereby achieving the goal of reducing the ethyl carbamate content in wine fermentation, but the above scheme does not disclose a method for effectively controlling the EC content in dry white wine to ensure the quality and safety of the wine. Summary of the invention

[0004] Technical purpose: In order to overcome the deficiencies in the prior art, the present invention provides a method for controlling the ethyl carbamate content in dry white wine.

[0005] Technical solution: To achieve the above purpose, the method for controlling the ethyl formate content in dry white wine disclosed in the present invention comprises the following steps: S1: Grape cultivation: Apply organic fertilizers in the vineyard and reduce the use of urea; S2: Determination of the harvest period: After the grapes change color, samples are taken every 3 to 5 days to measure the changes in sugar and acid indicators of the grapes, and sensory tasting is performed to determine the grape harvest period. The sugar content of the grapes is 190 to 210 g / L in terms of glucose, the total acid is 5.5 to 7.0 g / L in terms of tartaric acid, and the amino nitrogen content of the grapes is 150 to 300 mg / L. S3: Harvesting: Grapes are harvested manually in the morning or evening when the temperature is low. Grapes must be fresh, with loose clusters and good coloring. Diseased, rotten, moldy, and green grapes must not be picked. After the grapes are harvested, dry ice is sprinkled in the transport basket for cooling and protection, and the grapes are transported to the processing station within 2 hours. S4: grape bunch selection: putting the grapes picked in step S3 on a conveyor belt for manual grape bunch selection, removing grape bunches, fruit stems and leaves with uneven coloring, diseased and rotten fruits, moldy fruits and green fruits; S5: Destemming: Softly remove the stems of the grapes, keeping more than 90% of the grapes intact; S6: Grain sorting: The berries are sorted manually or optically to remove diseased and rotten berries, green berries, stalks and leaves; S7: Crushing: Slightly crushing the fruit particles sorted in step S6, adding sulfur dioxide and pectinase during the crushing process, and adding dry ice for cooling and protection; S8: Cooling and juice extraction: The crushed grapes are quickly cooled by a heat exchanger, and then put into an air bag press to extract juice, and protective gas is introduced during the juice extraction process; S9: Low temperature clarification: put the grape juice into the tank for clarification. The tank is pre-cooled and the protective gas is passed into the tank to exhaust the air. The grape juice is put into the tank. After the tank is full, add bentonite for clarification and let it stand until it is clear. S10: Juice separation and temperature recovery: the upper clarified grape juice is poured back and separated, and the clarified grape juice is heated to 12-14°C; S11: Low-temperature alcohol fermentation: The clarified grape juice is inoculated with brewer's yeast for dry white fermentation for fermentation. No yeast nutritional additives are added during the fermentation process. The fermentation temperature is 14-16°C and the fermentation time is 10-20 days. S12: Tank decanting: monitor the specific gravity and temperature of the grape juice during alcoholic fermentation. When the residual sugar content is lower than 4g / L, lower the temperature of the wine to 10-12°C, decant to remove the coarse lees, and add sulfur dioxide. There is no need to carry out malic acid-lactic acid fermentation. S13: Low temperature storage: The wine is stored at a temperature of 10-15°C, free sulfur dioxide is controlled at 30-40 mg / L, and protective gas is filled into the tank; S14: Detection: Detect the urea content in the wine to ensure that the urea content is below 5 mg / L; S15: Clarification: The wine temperature is controlled at 10-15℃; S16: Freezing: putting the wine in step S15 into a freezing tank and cooling it to -5 to -4°C, adding 0.1 to 0.2 g / L of seed crystals and keeping it warm for 4 to 8 days, and circulating protective gas from the bottom of the tank for 5 minutes every day; S17: Filtration: Filter the wine using a filtration device under heat preservation conditions; S18: Sterilization: sterilize the wine through a membrane filtration device; S19: Inspect the wine for physical and chemical indicators, microbiological indicators, and sensory evaluation. Fill the wine after passing the inspection and evaluation. Control the temperature within 20℃ after bottling.

[0006] Preferably, in step S7, the fruit crushing rate is 60-70%, the amount of sulfur dioxide added is 60-80 mg / L, and the amount of pectinase added is 20-30 mg / L.

[0007] Preferably, in step S8, the temperature of the crushed grapes after cooling by the heat exchanger is 3-5° C., and the juice yield is controlled at 40-60%.

[0008] Preferably, the grape juice is cooled down while being put into the tank in step S9, the temperature of the grape juice is maintained at 3-5° C., and the amount of bentonite added is 0.1-0.5 g / L.

[0009] Preferably, the amount of yeast in step S11 is not less than 10 6 cfu / mL, alcohol content: 11-12% v / v.

[0010] Preferably, in step S12, when the specific gravity drops to 0.997, sampling is required every 12 hours to detect the sugar content, and the amount of sulfur dioxide added is 50-80 mg / L.

[0011] Preferably, in step S14, if the urea content of the wine exceeds 5 mg / L, 30-50 mg / L urease needs to be added for treatment.

[0012] Preferably, the membrane filtration equipment in step S18 is a two-stage membrane filtration, the pore size of the first-stage filtration membrane is 0.45 microns, and the pore size of the second-stage filtration membrane is 0.20 microns.

[0013] Preferably, the grape variety is Chardonnay, Riesling, Guiana, Sauvignon Blanc, Pinot Blanc or Viognier.

[0014] The beneficial effects of the present invention are: 1. The method for controlling the ethyl formate content in dry white wine disclosed in the present invention covers the entire winemaking process from grape raw materials, fermentation of raw wine, aging, etc., and is a systematic solution. By reducing the use of nitrogen fertilizers such as urea during grape planting, the amino nitrogen content in the fruit is controlled within a reasonable range, and the sugar content and total acid index in the maturity index are monitored during grape harvest to avoid over-ripening of the fruit.

[0015] 2. During the fermentation process, fermentation aids, yeast nutrients and other methods are not used to control the growth of ethyl carbamate. The limit value of urea content in raw wine is clarified, and a method of reducing the urea content in raw wine by treating it with urease produced by specific bacteria is given. The temperature control range of each stage such as fermentation, storage, aging and bottling is further clarified. Through a combination of measures in the entire process of dry white wine brewing, the content of ethyl carbamate is controlled within the standard limit. DETAILED DESCRIPTION

[0016] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0017] Example 1: A method for controlling the ethyl carbamate content in dry white wine, comprising the following steps: S1: Planting of grapes: organic fertilizer is applied to the vineyard to reduce the use of urea; the grape variety can be one of Chardonnay, Riesling, Guiness, Sauvignon Blanc, Pinot Blanc, and Viognier. The grape variety selected in this embodiment is Chardonnay.

[0018] S2: Determination of the harvest period: After the grapes change color, samples are taken every 3 days to measure the changes in the sugar and acid indicators of the grapes, and sensory tasting is performed. The sugar content of the grapes is 190g / L in terms of glucose, the total acid is 7.0g / L in terms of tartaric acid, and the grape amino nitrogen content is 150mg / L.

[0019] S3: Harvesting: Grapes are harvested manually in the morning when the temperature is low. The grapes must be fresh, with loose clusters and good coloring. During the picking process, diseased, moldy, and green grapes must not be picked. After the grapes are harvested, dry ice is sprinkled in the transport basket for cooling and protection, and the grapes are transported to the processing station within 2 hours.

[0020] S4: Grape bunch selection: The grapes picked in step S3 are placed on a conveyor belt for manual bunch selection to remove grape bunches, fruit stems, leaves and other debris with uneven coloring, diseased and rotten fruits, moldy fruits, and green fruits.

[0021] S5: Destemming: Softly remove the stems of the grapes, keeping more than 90% of the grapes intact.

[0022] S6: Grape sorting: The grape berries are optically sorted to remove diseased and rotten berries, green berries, stalks, leaves and other debris.

[0023] S7: Crushing: The fruit particles sorted in step S6 are lightly crushed, with a crushing rate of 60%. During the crushing process, 60 mg / L of sulfur dioxide and 20 mg / L of pectinase are added, and dry ice is added for cooling and protection.

[0024] S8: Cooling and juice extraction: The crushed grapes are rapidly cooled to 3°C by a heat exchanger, and then put into an air bag press to extract juice. The juice yield is controlled at 40%, and protective gas is introduced during the juice extraction process. In this embodiment, the heat exchanger is a shell and tube heat exchanger, and the protective gas is carbon dioxide gas.

[0025] S9: low temperature clarification: put the grape juice into the tank for clarification, pre-cool the tank in advance and introduce protective gas to exhaust air, put the grape juice into the tank, and start cooling the grape juice while entering the tank, keep the temperature of the grape juice at 3°C, add 0.1g / L bentonite to clarify after the tank is full, and let it stand until it is clarified; in this embodiment, the protective gas is carbon dioxide gas.

[0026] S10: Juice separation and temperature return: the upper clarified grape juice after clarification is poured back and separated, and the clarified grape juice is returned to the temperature of 12°C.

[0027] S11: Low temperature alcohol fermentation: The clarified grape juice is inoculated with brewer's yeast for dry white fermentation for fermentation. No yeast nutritional additives are added during the fermentation process. The number of yeasts is not less than 10 6 cfu / mL, fermentation temperature: 14°C, fermentation time: 20 days, alcohol content: 11% v / v.

[0028] S12: Decanting: Monitor the specific gravity and temperature of the grape juice during alcoholic fermentation. When the specific gravity drops to 0.997, samples should be taken every 12 hours to test the sugar content. When the residual sugar in fermentation is lower than 4g / L, the wine temperature should be lowered to 10°C, the tank should be decanted to remove the coarse lees, and 50mg / L sulfur dioxide should be added. There is no need for malic acid-lactic acid fermentation.

[0029] S13: Low temperature storage: The wine of step S12 is stored at a temperature of 10°C, free sulfur dioxide is controlled to 30 mg / L, and a protective gas is filled into the tank; in this embodiment, the protective gas is carbon dioxide gas.

[0030] S14: Detection: Detect the urea content in the wine to ensure that the urea content is 5mg / L.

[0031] S15: Clarification: The wine temperature is controlled at 10℃.

[0032] S16: Freezing: The wine from step S15 is placed in a freezing tank and quickly cooled to -5°C. 0.1 g / L of seed crystals is added and kept warm for 4 days. A protective gas is circulated from the bottom of the tank and stirred for 5 minutes every day. The freezing time is 4 days.

[0033] S17: Filtration: Filter the wine under heat preservation conditions using a filtration device; the filtration device may be a plate and frame filtration device, or a cross-flow filtration device well known to those skilled in the art.

[0034] S18: Sterilization: sterilize the wine by passing it through a membrane filtration device; wherein the membrane filtration device is a two-stage membrane filtration device, the pore size of the first stage filtration membrane is 0.45 microns, and the pore size of the second stage filtration membrane is 0.20 microns.

[0035] S19: inspect the wine for physical and chemical indicators, microbiological indicators, and sensory evaluation, and fill it after it passes the inspection and evaluation. After bottling, the temperature is controlled within 20° C. In this embodiment, the temperature is controlled at 20° C. after bottling.

[0036] Embodiment 2: The method for controlling the ethyl formate content in dry white wine comprises the following steps: S1: Planting of grapes: organic fertilizer is applied to the vineyard to reduce the use of urea; the grape variety can be one of Chardonnay, Riesling, Guiness, Sauvignon Blanc, Pinot Blanc, and Viognier. The grape variety selected in this embodiment is Riesling.

[0037] S2: Determination of the harvest period: After the grapes change color, samples are taken every 5 days to measure the changes in sugar and acid indexes of the grapes, and sensory tasting is performed to determine the grape harvest period. The sugar content of the grapes is 210g / L in terms of glucose, the total acid is 5.5g / L in terms of tartaric acid, and the amino nitrogen content of the grapes is 300mg / L; S3: Harvesting: Grapes are harvested manually in the morning when the temperature is low. The grapes must be fresh, with loose clusters and good coloring. Diseased, moldy, and green grapes must not be picked. After the grapes are harvested, dry ice is sprinkled in the transport basket for cooling and protection, and the grapes are transported to the processing station within 2 hours.

[0038] S4: Grape bunch selection: The grapes picked in step S3 are placed on a conveyor belt for manual bunch selection to remove impurities such as grape bunches, fruit stems and leaves with uneven coloring, diseased and rotten fruits, moldy fruits, and green fruits.

[0039] S5: Destemming: Softly remove the stems of the grapes, keeping more than 90% of the grapes intact.

[0040] S6: Grain sorting: The fruit grains are optically sorted to remove impurities such as diseased and rotten fruit grains, green fruit grains, fruit stems and leaves. S7: Crushing: The fruit particles sorted in step S6 are slightly crushed, with a crushing rate of 70%. During the crushing process, 80 mg / L of sulfur dioxide and 30 mg / L of pectinase are added, and dry ice is added for cooling and protection.

[0041] S8: Cooling and juice extraction: The crushed grapes are rapidly cooled to 5°C via a heat exchanger, and then put into an air bag press to extract juice. The juice yield is controlled at 60%, and protective gas is introduced during the juice extraction process. In this embodiment, the heat exchanger is a shell-and-tube heat exchanger, and the protective gas is carbon dioxide gas.

[0042] S9: low temperature clarification: put the grape juice into the tank for clarification, pre-cool the tank in advance and introduce protective gas to exhaust air, put the grape juice into the tank, and start cooling the grape juice while entering the tank, keep the temperature of the grape juice at 5°C, add 0.5g / L bentonite to clarify after the tank is full, and let it stand until it is clarified; in this embodiment, the protective gas is carbon dioxide gas.

[0043] S10: Juice separation and temperature return: the upper clarified grape juice after clarification is poured back and separated, and the clarified grape juice is temperature returned to 14°C.

[0044] S11: Low temperature alcohol fermentation: The clarified grape juice is inoculated with brewer's yeast for dry white fermentation for fermentation. No yeast nutritional additives are added during the fermentation process. The number of yeasts is not less than 10 6 cfu / mL, fermentation temperature: 16°C, fermentation time: 10 days, alcohol content: 12% v / v.

[0045] S12: Decanting: Monitor the specific gravity and temperature of the grape juice during alcoholic fermentation. When the specific gravity drops to 0.997, samples should be taken every 12 hours to test the sugar content. When the residual sugar in fermentation is lower than 4g / L, the wine temperature should be lowered to 12°C, the tank should be decanted to remove the coarse lees, and 80mg / L sulfur dioxide should be added. There is no need for malic acid-lactic acid fermentation.

[0046] S13: Low temperature storage: The wine storage temperature is 15°C, the free sulfur dioxide is controlled at 40 mg / L, and a protective gas is filled into the tank; in this embodiment, the protective gas is carbon dioxide gas.

[0047] S14: Detection: Detect the urea content in the wine and ensure that the urea content is 4mg / L.

[0048] S15: Clarification: The wine temperature is controlled at 15℃; S16: Freezing: The wine from step S15 is placed in a freezing tank and quickly cooled to -4°C. 0.2 g / L of seed crystals are added to keep the temperature for 8 days. A protective gas is circulated from the bottom of the tank and stirred for 5 minutes every day. The freezing time is 8 days.

[0049] S17: Filtration: Filter the wine under heat preservation conditions using a filtration device; the filtration device may be a plate and frame filtration device, or a cross-flow filtration device well known to those skilled in the art.

[0050] S18: Sterilization: sterilize the wine by passing it through a membrane filtration device; wherein the membrane filtration device is a two-stage membrane filtration device, the pore size of the first stage filtration membrane is 0.45 microns, and the pore size of the second stage filtration membrane is 0.20 microns.

[0051] S19: Check the physical and chemical indicators, microbiological indicators and sensory evaluation of the wine. Fill it after passing the inspection and evaluation. Control the temperature at 19℃ after bottling.

[0052] Example 3: A method for controlling the ethyl carbamate content in dry white wine, comprising the following steps: S1: Planting of grapes: organic fertilizer is applied to the vineyard to reduce the use of urea; the grape variety can be one of Chardonnay, Riesling, Guiness, Sauvignon Blanc, Pinot Blanc, and Viognier. The grape variety selected in this embodiment is Chardonnay.

[0053] S2: Determination of the harvest period: After the grapes change color, samples are taken every 4 days to measure the changes in sugar and acid indexes of the grapes, and sensory tasting is performed to determine the grape harvest period. The sugar content of the grapes is 205g / L in terms of glucose, the total acid is 6.2g / L in terms of tartaric acid, and the amino nitrogen content of the grapes is 210mg / L; S3: Harvesting: Grapes are harvested manually in the evening when the temperature is low. The grapes must be fresh, with loose clusters and good coloring. Diseased, moldy, and green grapes must not be picked. After the grapes are harvested, dry ice is sprinkled in the transport basket for cooling and protection, and the grapes are transported to the processing station within 2 hours.

[0054] S4: Grape bunch selection: The grapes picked in step S3 are placed on a conveyor belt for manual bunch selection to remove impurities such as grape bunches, fruit stems and leaves with uneven coloring, diseased and rotten fruits, moldy fruits, and green fruits.

[0055] S5: Destemming: Softly remove the stems of the grapes, keeping more than 90% of the grapes intact.

[0056] S6: Grain selection: The fruit grains are manually selected to remove diseased and rotten fruit grains, green fruit grains, fruit stems and leaves and other impurities.

[0057] S7: Crushing: The fruit particles sorted in step S6 are slightly crushed, with a crushing rate of 65%. During the crushing process, 70 mg / L of sulfur dioxide and 25 mg / L of pectinase are added, and dry ice is added for cooling and protection.

[0058] S8: Cooling and juice extraction: The crushed grapes are rapidly cooled to 4°C via a heat exchanger, and then put into an air bag press to extract juice. The juice yield is controlled at 50%, and protective gas is introduced during the juice extraction process. In this embodiment, the heat exchanger is a shell and tube heat exchanger, and the protective gas is carbon dioxide gas.

[0059] S9: low temperature clarification: put the grape juice into the tank for clarification, pre-cool the tank in advance and introduce protective gas to exhaust air, put the grape juice into the tank, and start cooling the grape juice while putting it into the tank, keep the temperature of the grape juice at 4°C, add 0.3g / L bentonite to clarify after the tank is full, and let it stand until it is clarified; in this embodiment, the protective gas is carbon dioxide gas.

[0060] S10: Juice separation and temperature return: the upper clarified grape juice after clarification is poured back and separated, and the clarified grape juice is returned to the temperature of 13°C.

[0061] S11: Low temperature alcohol fermentation: The clarified grape juice is inoculated with brewer's yeast for dry white fermentation for fermentation. No yeast nutritional additives are added during the fermentation process. The number of yeasts is not less than 10 6 cfu / mL, fermentation temperature: 15℃, fermentation time: 15 days, alcohol content: 11.7%v / v.

[0062] S12: Decanting: Monitor the specific gravity and temperature of the grape juice during alcoholic fermentation. When the specific gravity drops to 0.997, samples should be taken every 12 hours to test the sugar content. When the residual sugar in fermentation is lower than 4g / L, the wine temperature should be lowered to 11°C, the tank should be decanted to remove the coarse lees, and 60mg / L sulfur dioxide should be added. There is no need for malic acid-lactic acid fermentation.

[0063] S13: Low temperature storage: The wine storage temperature is 13°C, the free sulfur dioxide is controlled at 35 mg / L, and a protective gas is filled into the tank; in this embodiment, the protective gas is carbon dioxide gas.

[0064] S14: Detection: The urea content in the wine is detected to be 8.5 mg / L. To ensure that the urea content is below 5 mg / L, 30-50 mg / L urease needs to be added for treatment.

[0065] In Example 3, in order to verify the inhibitory effect of urease on ethyl carbamate (EC), two ureases (labeled as 1# and 2#) were selected to experiment on the above-mentioned wine with a urea content of 8.5 mg / L. In this example, 1# urease was produced by the microbial strain SST7, and 2# urease was produced by the microbial strain YXT5. Urease is an enzyme well known to those skilled in the art and will not be described in detail here. The amount of urease added was 30 mg / L. The results of the inhibition of the growth of ethyl carbamate (EC) are detailed in Table 1.

[0066] In Example 4, two ureases (labeled as 1# and 2#) were selected to experiment on the above-mentioned wine with a urea content of 8.5 mg / L. In this example, 1# urease was produced by the microbial strain SST7, and 2# urease was produced by the microbial strain YXT5. Urease is an enzyme well known to those skilled in the art and will not be described in detail here. The amount of urease added was 40 mg / L. The results of the inhibition of ethyl carbamate (EC) growth are detailed in Table 1.

[0067] In Example 5, two ureases (labeled as 1# and 2#) were selected to experiment on the above-mentioned wine with a urea content of 8.5 mg / L. In this example, 1# urease was produced by the microbial strain SST7, and 2# urease was produced by the microbial strain YXT5. Urease is an enzyme well known to those skilled in the art and will not be described in detail here. The amount of urease added was 50 mg / L. The results of the inhibition of ethyl carbamate (EC) growth are detailed in Table 1.

[0068] In Example 6, in order to prove that urease still has an inhibitory effect on the growth of ethyl carbamate (EC) in wine containing high concentration of urea, 100 mg / L urea was added to the above-mentioned wine with a urea content of 8.5 mg / L to obtain a wine with a urea content of 108.5 mg / L. Two ureases (labeled as 1# and 2#) were selected to conduct experiments on the above-mentioned wine with a urea content of 108.5 mg / L. In this example, 1# urease was produced by microbial strain SST7, and 2# urease was produced by microbial strain YXT5. Urease is an enzyme well known to those skilled in the art and will not be described in detail here. The amount of urease added was 50 mg / L. The results of the inhibition of the growth of ethyl carbamate (EC) are shown in Table 1.

[0069] In Comparative Example 1, the wine with a urea content of 8.5 mg / L was subjected to an experiment without adding urease. The results of ethyl carbamate (EC) growth are shown in Table 1.

[0070] In Comparative Example 2, the wine with a urea content of 108.5 mg / L was subjected to an experiment without adding urease. The results of ethyl carbamate (EC) growth are shown in Table 1.

[0071] S15: Clarification: The wine temperature is controlled at 13°C; S16: Freezing: The wine in step S15 is placed in a freezing tank and quickly cooled to -4.5°C, 0.15 g / L of seed crystals are added and kept warm for 6 days, and protective gas is circulated from the bottom of the tank for 5 minutes every day for stirring, and the freezing time is 6 days; S17: Filtration: Filter the wine under heat preservation conditions using a filtration device; the filtration device may be a plate and frame filtration device, or a cross-flow filtration device well known to those skilled in the art.

[0072] S18: Sterilization: sterilize the wine by passing it through a membrane filtration device; wherein the membrane filtration device is a two-stage membrane filtration device, the pore size of the first stage filtration membrane is 0.45 microns, and the pore size of the second stage filtration membrane is 0.20 microns.

[0073] S19: Inspect the wine for physical and chemical indicators, microbiological indicators, and sensory evaluation. Fill the wine after passing the inspection and evaluation. Control the temperature at 18°C ​​after bottling.

[0074] Table 1: Effect of urease treatment on the growth of urea and ethyl carbamate (EC) in dry white wine

[0075] Note: “ND” means not detected.

[0076] It can be seen from the experimental results of Examples 1 to 6 in Table 1 that the generation or growth of ethyl carbamate (EC) in dry white wine treated with urease #1 and urease #2 can be effectively inhibited, and the content of ethyl carbamate (EC) is controlled within the range of 0 to 10 μg·L -1 range, and can significantly reduce the urea content, and 1# urease has the best effect; when the urea content in dry white wine is lower than 5 mg / L, the generation or growth of ethyl carbamate (EC) falls within the range of 0-10 μg·L -1 It can be seen from Comparative Examples 1 and 2 that when the urea content is higher than 5 mg / L, the growth of ethyl carbamate (EC) in dry white wine without urease treatment has an accelerated trend under the premise of high urea content, high storage temperature and long storage time. Under the condition of high urea concentration (adding 100 mg / L urea), the ethyl carbamate (EC) content in Comparative Example 2 increased to 105.8 μg·L after one month. -1 In Example 6, after high-concentration urea was treated with urease #1 for one month, the urea concentration dropped to 1.2 mg·L -1 , ethyl carbamate (EC) was not detected. After one month of treatment with 2# urease, urea was reduced to 10.3 mg / L, and the content of ethyl carbamate (EC) was 8.5 μg·L -1 , which is only 105.8 μg·L in Comparative Example 2 -1 As can be seen from Table 1, when the urea content in the wine is lower than 5 mg / L, or the degradation of high-content urea by urease treatment has a significant effect on controlling the growth of ethyl carbamate (EC). This method reduces the use of nitrogen fertilizers such as urea during the planting process, controls the amino nitrogen content in the fruit, and controls the temperature at each stage after fermentation, aging, and bottling during the entire process of dry white winemaking. It clarifies the limit of urea content in the original wine and provides urease treatment to inhibit the growth of ethyl carbamate and effectively control its content in dry white wine.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the ethyl carbamate content in dry white wine, characterized in that: The following steps are involved: S1: Grape cultivation: Apply organic fertilizers in the vineyard and reduce the use of urea; S2: Determination of the harvest period: After the grapes change color, samples are taken every 3 to 5 days to measure the changes in sugar and acid indicators of the grapes, and sensory tasting is performed to determine the grape harvest period. The sugar content of the grapes is 190 to 210 g / L in terms of glucose, the total acid is 5.5 to 7.0 g / L in terms of tartaric acid, and the amino nitrogen content of the grapes is 150 to 300 mg / L. S3: Harvesting: Grapes are harvested manually in the morning or evening when the temperature is low. Grapes must be fresh, with loose clusters and good coloring. Diseased, rotten, moldy, and green grapes must not be picked. After the grapes are harvested, dry ice is sprinkled in the transport basket for cooling and protection, and the grapes are transported to the processing station within 2 hours. S4: grape bunch selection: putting the grapes picked in step S3 on a conveyor belt for manual grape bunch selection, removing grape bunches, fruit stems and leaves with uneven coloring, diseased and rotten fruits, moldy fruits and green fruits; S5: Destemming: Softly remove the stems of the grapes, keeping more than 90% of the grapes intact; S6: Grain sorting: The berries are sorted manually or optically to remove diseased and rotten berries, green berries, stalks and leaves; S7: Crushing: Slightly crushing the fruit particles sorted in step S6, adding sulfur dioxide and pectinase during the crushing process, and adding dry ice for cooling and protection; S8: Cooling and juice extraction: The crushed grapes are quickly cooled by a heat exchanger, and then put into an air bag press to extract juice, and protective gas is introduced during the juice extraction process; S9: Low temperature clarification: put the grape juice into the tank for clarification. The tank is pre-cooled and the protective gas is passed into the tank to exhaust the air. The grape juice is put into the tank. After the tank is full, add bentonite for clarification and let it stand until it is clear. S10: Juice separation and temperature recovery: the upper clarified grape juice is poured back and separated, and the clarified grape juice is heated to 12-14°C; S11: Low-temperature alcohol fermentation: The clarified grape juice is inoculated with brewer's yeast for dry white fermentation for fermentation. No yeast nutritional additives are added during the fermentation process. The fermentation temperature is 14-16°C and the fermentation time is 10-20 days. S12: Tank decanting: monitor the specific gravity and temperature of the grape juice during alcoholic fermentation. When the residual sugar content is lower than 4g / L, lower the temperature of the wine to 10-12°C, decant to remove the coarse lees, and add sulfur dioxide. There is no need to carry out malic acid-lactic acid fermentation. S13: Low temperature storage: The wine is stored at a temperature of 10-15°C, free sulfur dioxide is controlled at 30-40 mg / L, and protective gas is filled into the tank; S14: Detection: Detect the urea content in the wine to ensure that the urea content is below 5 mg / L; S15: Clarification: The wine temperature is controlled at 10-15℃; S16: Freezing: putting the wine from step S15 into a freezing tank and cooling it to -5 to -4°C, adding 0.1 to 0.2 g / L of seed crystals and keeping it warm for 4 to 8 days, and circulating protective gas from the bottom of the tank for 5 minutes every day; S17: Filtration: Filter the wine using a filtration device under heat preservation conditions; S18: Sterilization: sterilize the wine through a membrane filtration device; S19: Inspect the wine for physical and chemical indicators, microbiological indicators, and sensory evaluation. Fill the wine after passing the inspection and evaluation. Control the temperature within 20℃ after bottling.

2. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: In step S7, the fruit particle crushing rate is 60-70%, the amount of sulfur dioxide added is 60-80 mg / L, and the amount of pectinase added is 20-30 mg / L.

3. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: In the step S8, the temperature of the crushed grapes after being cooled by the heat exchanger is 3-5° C., and the juice yield is controlled at 40-60%.

4. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: In step S9, the grape juice is put into the tank and cooled down to keep the temperature of the grape juice at 3-5° C. The amount of bentonite added is 0.1-0.5 g / L.

5. The method for controlling the ethyl carbamate content in dry white wine according to claim 1, characterized in that: The number of yeast in step S11 is not less than 10 6 cfu / mL, alcohol content: 11-12% v / v.

6. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: In step S12, when the specific gravity drops to 0.997, sampling is required every 12 hours to detect the sugar content, and the amount of sulfur dioxide added is 50-80 mg / L.

7. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: In step S14, if the urea content of the wine exceeds 5 mg / L, 30-50 mg / L urease needs to be added for treatment.

8. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: The membrane filtration equipment in step S18 is a two-stage membrane filtration, the pore size of the first-stage filtration membrane is 0.45 microns, and the pore size of the second-stage filtration membrane is 0.20 microns.

9. The method for controlling the ethyl formate content in dry white wine according to claim 1, characterized in that: The grape variety is Chardonnay, Riesling, Guiana, Sauvignon Blanc, Pinot Blanc or Viognier.

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