A process for reducing the alcohol content and acidity of baijiu (Chinese liquor)

Abstract

This invention discloses a process for reducing the alcohol content and acidity of baijiu (Chinese white liquor), belonging to the field of baijiu processing technology. The method involves nanofiltration of the base liquor, collecting the retentate and permeate separately; distilling and de-alcoholizing the permeate, and adding 1%–15% of the first fraction (by volume of the permeate) back to the distillation residue; preparing a pre-combined sample from the retentate and distillation residue, and determining whether acid reduction is necessary based on sensory evaluation and acid-ester detection results. When acid reduction is required, part or all of the distillation residue is neutralized with MgO, Ca(OH)2, or MgCO3, followed by nanofiltration to collect the acid-reduced permeate. The retentate and the corresponding treated distillation residue components are combined, water is added to the target alcohol content, filtration is performed to remove turbidity, and blending is carried out to obtain reduced-alcohol and reduced-acid baijiu. This method, through nanofiltration and permeate treatment, reduces the loss of flavor components during the alcohol reduction process and adjusts the acidity of the liquor requiring acid reduction, thereby achieving alcohol reduction, flavor preservation, and acid-ester balance.

Description

Technical Field

[0001] This invention relates to a process for reducing the alcohol content and acidity of baijiu (Chinese liquor), belonging to the field of baijiu processing technology. Background Technology

[0002] When producing finished baijiu (Chinese white liquor) with the target alcohol content, the base liquor usually needs to be diluted. Traditional dilution with water reduces the concentration of flavor components per unit volume of liquor and may cause problems such as turbidity, diluted flavor, or excessive sourness. For baijiu with lower alcohol content, how to retain flavor while reducing alcohol content and harmonizing the acid-ester ratio is a problem that the dilution process needs to solve.

[0003] The flavor components of baijiu include organic acids, esters, aldehydes, higher alcohols, and related components formed during aging. These components differ in molecular size, volatility, solubility, and thermal stability. Lactic acid, acetic acid, butyric acid, hexanoic acid, and their corresponding ethyl esters are small-molecule flavor components of interest in this method. This method utilizes nanofiltration to separate different components, retaining the flavor components that can be retained in the nanofiltration retentate. Only the nanofiltration permeate is subjected to distillation and acid reduction to avoid the destruction of the retained flavor components through heating and distillation. The first fraction is added back to minimize the loss of flavor components.

[0004] Publication WO2004113489A1 describes a process for separating alcoholic beverages using nanofiltration, followed by distillation of the permeate for alcohol removal, and recombination of the alcohol-free liquid with the retained portion. It also mentions the removal of all or part of ionic components from the permeate after alcohol removal. This publication indicates its applicability to the alcohol removal of fermented beverages such as wine, beer, cider, mead, and sake. The nanofiltration alcohol removal method is widely used for reducing the alcohol content of fermented beverages, and the permeate can be redistilled and added back to replenish flavor. Baijiu (Chinese white liquor) is a distilled spirit with small flavor molecules; nanofiltration has no alcohol removal effect, and redistillation results in the loss of both ethanol and flavor. Therefore, for reducing the alcohol content of baijiu, it is still necessary to address the recovery of volatile flavor components and the acidity balance after alcohol removal, taking into account the characteristics of the liquor. In this method, after nanofiltration splitting, the permeate undergoes rectification for alcohol removal, and a specified proportion of the initial fraction is added back, pre-combination evaluation is performed, and neutralization of the rectification residue is combined with nanofiltration desalination as needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a process for reducing the alcohol content and acidity of baijiu by distillation and de-alcoholization, so as to reduce flavor loss and harmonize acid and esters during the alcohol reduction process.

[0006] This invention employs a nanofiltration separation, permeate distillation for alcohol removal, and on-demand nanofiltration desalination and acid reduction process, comprising the following steps: (1) Nanofiltration is performed on the base wine, and the nanofiltration retentate and nanofiltration permeate are collected separately, so that the flavor components that can be retained by the nanofiltration membrane are retained in the retentate; (2) Based on the volume of the base liquor, the alcohol content of the base liquor, the target alcohol content, and the target liquor volume, the theoretical estimation of the de-alcoholization parameters is performed according to Equations 1 to 4. The nanofiltration permeate is distilled, and the first fraction and the fraction used to remove ethanol are collected separately. The volume of the first fraction accounts for 1% to 15% of the volume of the nanofiltration permeate and is added back to the distillation residue after the distillation is completed to reduce the loss of flavor components such as ethyl acetate. The fraction used to remove ethanol is not added back.

[0007] (Equation 1) (Equation 2) (Equation 3) (Equation 4) In the formula, V0 is the volume of base wine, V1 is the volume of pure ethanol to be removed by distillation, V2 is the volume of the dealcoholized fraction that is not added back, V3 is the volume of nanofiltration permeate, V4 is the volume of nanofiltration retentate, and V t The target volume of the liquor is given in liters (L); φ0, φ1, φ2, φ3, φ4, φ t The figures represent the ethanol volume fractions of the base liquor, the non-recycled dealcoholized fraction, the rectification residue after recycling the initial fraction, the nanofiltration permeate, the nanofiltration retentate, and the target liquor, respectively, and are expressed as decimals when substituted into the formula. ρ1, ρ2, and ρ3 represent the densities of the dealcoholized fraction, the rectification residue after recycling the initial fraction, and the nanofiltration permeate, respectively, in kg / L. The above estimates are based on the conservation of ethanol and the mass conservation shown in Equation 3, neglecting losses from sampling, equipment holdup, evaporation, and subsequent removal by the high-salt retentate; the results represent the theoretical throughput. All volumes, alcohol content, and densities are based on the same temperature reference.

[0008] (3) Take the nanofiltration retentate and the distillation residue after adding the first distillate to prepare a pre-combined sample, conduct sensory evaluation and detect the total acid and total ester content, and determine whether to carry out acid reduction treatment based on the sensory evaluation results and the target acid-ester ratio; (4) When acid reduction is required, take part or all of the distillation residue, add one or more of MgO, Ca(OH)2, and MgCO3 for neutralization, and then perform nanofiltration desalination. Collect the acid-reduced permeate and the high-salt retentate separately. When acid reduction is not required, retain the distillation residue for mixing. (5) For wine that has undergone deacidification treatment, combine the nanofiltration retentate, deacidified permeate, and undeacidified distillate. If all distillate residues have undergone deacidification treatment, do not add undeacidified distillate residues. For wine that has not undergone deacidification treatment, combine the nanofiltration retentate and distillate residues. Add water to the target alcohol content to obtain the wine to be deturbided. (6) Filter to remove turbidity and obtain a clear wine; (7) Blend to obtain the finished product of reduced alcohol content liquor.

[0009] Furthermore, the nanofiltration process uses an organic solvent-resistant nanofiltration membrane with a molecular weight cutoff of 100–300 Da and a divalent salt removal rate of over 98%.

[0010] Furthermore, the alcohol content of the fraction used to remove ethanol is above 90% vol.

[0011] Further, samples were taken and mixed according to the volume ratio of nanofiltration retentate and distillation residue in the wine to be combined, water was added to the target alcohol content and filtered to remove turbidity, and 1-10 L of pre-combined samples were prepared.

[0012] Furthermore, the nanofiltration desalination and acid reduction process: a. For wines requiring acid reduction, estimate the target total acid, the theoretical minimum volume of the distillate to be treated, and the theoretical amount of neutralizing agent using formulas 5 to 7. (Equation 5) (Equation 6) (Equation 7) In the formula, A0 is the total acid of the pre-combined sample, A1 is the total acid of the distillation residue, and A t B represents the target total acid, in g / L; C represents the total esters in the pre-combined sample, in g / L; C represents the mass concentration ratio of the target total acid to the total esters, where C = 1 / r when the target ester-to-ester ratio is 1:r; V5 represents the theoretical minimum volume of the distillation residue to be treated, in L, and the actual volume taken should not be less than V5; V t The target volume of the liquor is expressed in liters (L); m is the theoretical amount of the corresponding neutralizing agent, expressed in grams (g); k is the mass conversion factor of the neutralizing agent relative to the total acidity calculated as acetic acid, taken as 0.333 for MgO, 0.617 for Ca(OH)2, and 0.700 for MgCO3 based on approximate relative molecular masses; δ is the proportion of total acid reduction undertaken by the neutralizing agent, taken as 0 to 1 when substituted into the formula, and the sum of all δ values ​​is 1 when used together. Equations 6 and 7 are used with A0 greater than A... t Estimate the ideal scenario where the neutralization equivalent is measured and the resulting salt is separated.

[0013] b. Take part or all of the distillation residue and add one or more of food-grade MgO, Ca(OH)2, and MgCO3 to neutralize it.

[0014] c. Perform nanofiltration desalination on the neutralized distillation residue. After the volume of the collected desalted permeate reaches 50% to 80% of the initial volume of the distillation residue to be treated, gradually add water to dilute the high-salt retentate and continue nanofiltration until the alcohol content of the high-salt retentate is less than 10% vol and the volume is no more than 20% of the initial volume of the distillation residue to be treated. Collect the desalted permeate.

[0015] This invention separates base liquor into retentate and permeate using nanofiltration. Only the permeate is distilled, thus avoiding further distillation of the retentate portion, which is primarily composed of aged aroma components. The first fraction is added back to the distillation residue to retain some of its flavor components. Based on the acidity and sensory results of the pre-combined samples, liquor requiring acid reduction undergoes neutralization and nanofiltration desalination. The corresponding liquor components are then combined and water is added to the target alcohol content. This process achieves de-alcoholization by removing the ethanol-rich fraction with low flavor component content through distillation. Aged aroma components are retained in the retentate, while small-molecule backbone components are retained in the distillation residue, and a subsequent water addition step is included. The test and sensory evaluation results listed in the examples illustrate the alcohol reduction effect under the corresponding base liquor and process conditions. Attached Figure Description

[0016] Figure 1 The process flow for reducing the alcohol content and acidity of baijiu (Chinese liquor). Detailed Implementation

[0017] Example 1: Production of 29% vol Special Aroma Baijiu using 60.5% vol base liquor 1000 L of 29% vol special aroma type ultra-low alcohol baijiu was prepared using 1000 L of 60.5% vol 8-year-old special aroma type base liquor, employing the aforementioned distillation de-alcoholization and nanofiltration desalination and acid reduction process. Before processing the base liquor, based on the conservation of ethanol volume, relevant alcohol reduction parameters were calculated using Equations 1, 2, 3, and 4: the ethanol removal volume was 315 L, and the alcohol content of the distillate fraction was controlled at 93% vol, so the volume of the distillate fraction was 338.7 L; the alcohol content of the distillate residue (including the back-added fraction) was set to 30% vol. Referring to the table, the density of the 93% vol distillate fraction at 20℃ was 0.819 kg / L, the density of the 30% vol distillate residue was 0.962 kg / L, and the density of the 60.5% vol nanofiltration permeate (since nanofiltration has a weak effect on ethanol retention, the alcohol content of the retentate and permeate can be the same as that of the base liquor in the calculation, the same below) was 0.908 kg / L. Therefore, the calculated volume of the nanofiltration permeate was 710 L, and the volume of the nanofiltration retentate was 290 L.

[0018] (1) The base wine was treated by nanofiltration (molecular weight cutoff 150 Da) and 290 L of retentate and 710 L of permeate were collected.

[0019] (2) The above permeate is distilled and the distillate fraction is controlled at 93% vol. The first part of the fraction, which accounts for 7% of the permeate volume, i.e. 49.7 L, is collected for later use. The dealcoholized fraction that is not added back is also collected. After the distillation is completed, the aforementioned reserved fraction is added back to the distillate residue.

[0020] (3) According to the volume ratio of the two liquids in the wine to be combined, the nanofiltration retentate and the distillation residue were mixed, water was added to reduce the concentration to 29% vol, ultrafiltration was used to remove turbidity, and 5 L of pre-combined sample was prepared. The pre-combined sample was found to have a prominent sour taste, with a total acidity of 1.88 g / L, a total ester content of 2.27 g / L, and an acid-ester ratio of 1:1.21. Acid reduction treatment was required. The target acid-ester ratio was set at 1:1.8. The total acidity of the distillation residue was detected to be 3.13 g / L. Based on the acid-base neutralization equivalent, the relevant treatment parameters for acid reduction were calculated by formulas 5, 6, and 7: the target total acidity of the finished wine was 1.26 g / L, the minimum treatment residue volume was 197.7 L, and two neutralizing agents, MgO and Ca(OH)2, were added to reduce the acidity by 40% and 60%, respectively. The calculated amount of MgO added was 82.4 g and the amount of Ca(OH)2 added was 229.1 g.

[0021] (4) Based on the calculation results, take 200 L of distillation residue and add 82.4 g MgO and 229.1 g Ca(OH)2 to neutralize and reduce acidity.

[0022] (5) The distillation residue after neutralization is desalted by nanofiltration. When the acid-reduced permeate is collected to about 150 L, the retentate is gradually diluted with water and nanofiltration desalting is continued to reduce the loss of ethanol and overall flavor. After treatment, the high-salt retentate is 30 L with an alcohol content of 8% vol. The ethanol loss caused by the high-salt retentate accounts for only 0.4% of the original base wine.

[0023] (6) Mix the nanofiltration retentate, the undiluted distillate residue, and the diluted permeate, add water to reduce the alcohol content to 29% vol, with a total volume of about 1000 L, to obtain a cloudy wine.

[0024] (7) Ultrafiltration removes turbidity to obtain a clear wine.

[0025] (8) Blend and optimize the flavor to obtain the finished product of reduced alcohol content baijiu.

[0026] Comparative Example 1

[0027] The base liquor described in Example 1 was diluted to 29% vol by adding water, ultrafiltered to remove turbidity, and blended and optimized to obtain a control sample.

[0028] Table 1. Physicochemical and sensory comparison between Example 1 and Comparative Example 1 Example 1 1.23 2.24 1:1.82 46.0 Clear and transparent, with an elegant aroma of grains and aging, a smooth and sweet taste, a well-balanced body, a noticeable body, and a clean finish. Comparative Example 1 0.82 1.32 1:1.61 28.6 Clear and transparent, with a pleasant aroma that is slightly musty and watery, and a rice-like fragrance. It is smooth on the palate, slightly acidic, and has a mild aftertaste. As shown in Table 1, the total ester content of the 29% vol special aroma type baijiu prepared by the distillation de-alcoholization and nanofiltration desalting and acid reduction process is 61% higher than that of the comparative example. The total acid and total ester content are also higher. The ester ratio of the example is well-balanced, with an elegant aroma, aged aroma and obvious body. In contrast, the comparative example has a watery and sour taste and a weaker aftertaste.

[0029] Related experimental data 1: Flavor comparison between nanofiltration treated retentate and permeate of aged base wine Take 10 L of the 8-year-old base wine described in Example 1, circulate it through a 150 Da nanofiltration membrane, collect 3 L of retentate and 7 L of permeate, and compare the physicochemical and sensory characteristics after nanofiltration separation.

[0030] Table 2. Flavor Comparison of Nanofiltration Retained Liquid and Permeate from Vintage Base Wines Table 2 shows that nanofiltration has a weaker retention effect on ethanol and overall acid-ester flavor components, but significant sensory differences are observed, especially in the color and aged aroma characteristics of the wine. This is because the molecular weights of the color and aged aroma components are relatively large, while the molecular weights of ethanol and major acid-ester components are smaller. Aged aroma is related to hydrogen bonding, complexation, and colloidal structure, and is sensitive to heating, distillation, and rectification. The method of this invention first separates the wine through nanofiltration to enrich and protect the precious aged aroma structure.

[0031] Related experimental data 2: Flavor composition of distillate and residual liquid after distillation of base liquor permeate

[0032] The base wine described in Example 1 was nanofiltered and split according to a volume ratio of retentate to permeate of 3:7. 5 L of permeate was taken for distillation, and the fraction was controlled at about 93% vol. Each fraction was 500 mL. Theoretically, all 6 fractions can be distilled to obtain alcohol. The fractions 1 to 6 were numbered N1 to N6 according to the fraction sequence.

[0033] Table 3 Flavor composition of distillate and residue from base liquor permeate distillation As shown in Table 3, distillation can highly enrich ethanol, but the initial fraction contains a high content of low-boiling-point components such as aldehydes and ethyl acetate. It is necessary to add these components back in a certain proportion according to the characteristics of the liquor's style. The middle fraction, which is mainly composed of ethanol and aroma, is used for de-alcoholization. Baijiu itself is produced by distillation, and secondary distillation has no actual de-alcoholization effect. Even with vacuum distillation, the boiling points of ethanol and flavor components decrease together, so there is still no de-alcoholization separation effect.

[0034] Related experimental data 3: Comparison of different degree reduction methods The base wine described in Example 1 was prepared into 29% vol wine samples using the method of the present invention (nanofiltration-distillation-refill-(pre-combination)-neutralization and acid reduction-nanofiltration desalination-combination-water replenishment), the traditional water addition and dilution method, and the "nanofiltration-distillation-refilling" method (refer to the published document WO2004113489A1, the liquid flow distribution and operation after refilling are the same as in Example 1). The physicochemical properties, main flavor components and sensory characteristics of the wine samples treated by different methods are shown in Table 2.

[0035] Table 4. Test results of different degradation treatment methods Total acid g / L 1.20 0.85 2.56 Total esters g / L 2.32 1.42 1.75 Acetic acid g / L 0.525 0.440 1.191 lactic acid g / L 0.893 0.766 1.508 Ethyl acetate g / L 1.147 0.745 0.479 Ethyl lactate g / L 0.825 0.722 1.258 Sensory characteristics The aroma is elegant and pleasant, with a mellow, aged fragrance; the taste is smooth and sweet, with a harmonious flavor profile. It has a light aroma, a watery taste, and a slightly sour taste. The flavor profile is predominantly sour and astringent, with a hint of alcoholic finish, resulting in a noticeably unbalanced flavor profile. As shown in Table 4, in Comparative Example 1, the traditional method of diluting alcohol with water resulted in the simultaneous dilution of alcohol and flavor components, leading to a weaker flavor and an imbalance of acid and ester components. The "nanofiltration-distillation-re-blending" method used for comparison was not suitable for the preparation of diluted baijiu because nanofiltration has a weak retention effect on ethanol and small molecular components in baijiu. Although the retained liquid could retain the aged aroma and some macromolecular components, the permeate was distilled, resulting in a large loss of ester flavor components. The distillate tail liquid of the re-blending had a high content of organic acids and ethyl lactate, and the baijiu was sour and astringent after re-blending. Therefore, this method was not suitable for the preparation of diluted baijiu. Comparative experiments of this method were not conducted in Examples 2 to 5.

[0036] The method of this invention uses nanofiltration to separate the retentate, which retains the heat-sensitive aged aroma components. Distillation further refines the flavor components of the permeate. The first fraction, containing low-boiling-point flavor components such as aldehydes and ethyl acetate, is added back, while the middle fraction, mainly composed of ethanol, is used for de-alcoholization. This process significantly preserves the overall flavor. A pre-combination experiment is then conducted to observe the acid-ester balance. The distillation residue is taken as needed, neutralized, and nanofiltration is used for desalting to reduce acidity. Finally, the mixture is combined and water is added to achieve acid reduction, flavor preservation, and acid-ester balance.

[0037] Example 2: Production of 29% vol strong-aroma baijiu using 62% vol base liquor

[0038] Strong-aroma baijiu uses ethyl hexanoate as its main aroma component. Since the aroma of ethyl hexanoate is more pronounced at low alcohol content, if the base liquor to low-alcohol finished product volume ratio is designed to be 1:1, the ethyl hexanoate content will be higher for ultra-low alcohol baijiu, and the finished product may have an artificial or ester-like taste. Therefore, the preparation is carried out at a yield of 1:1.5, that is, 1000 L of base liquor is used to prepare 1500 L of strong-aroma ultra-low alcohol baijiu.

[0039] 1500 L of 29% vol ultra-low alcohol strong-aroma baijiu was prepared using 1000 L of 62% vol 6-year-old strong-aroma base liquor. Before base liquor treatment, based on the law of conservation of ethanol volume, relevant alcohol reduction parameters were calculated with reference to Equations 1, 2, 3, and 4: the ethanol removal volume was 185 L, and the alcohol content of the rectification fraction was controlled at 94% vol, so the rectification fraction volume was 196.8 L; the control alcohol content of the rectification residue (including the back-added fraction) was set at 33% vol. Referring to the table, the density of the 94% vol rectification fraction at 20℃ was 0.815 kg / L, the density of the 33% vol rectification residue was 0.958 kg / L, and the density of the 62% vol nanofiltration permeate was 0.904 kg / L. The calculated nanofiltration permeate volume was 420.4 L and the nanofiltration cutoff volume was 579.6 L.

[0040] (1) The base wine was treated by nanofiltration (molecular weight cutoff 150 Da) and 579.6 L of retentate and 420.4 L of permeate were collected.

[0041] (2) The above permeate is distilled to control the distillate fraction at 94% vol. The fraction in the first stage of distillation is rich in ethyl acetate. By appropriately reducing the recovery ratio of the first stage fraction, the "increase in ethyl acetate and decrease in ethyl acetate" can be achieved. Therefore, 12.6 L of the fraction in the first stage, which accounts for 3% of the permeate volume, is collected for later use. Another 196.8 L of the dealcoholized fraction that is not added back is collected. After the distillation is completed, the aforementioned reserved fraction is added back to the distillate residue.

[0042] (3) According to the volume ratio of the two liquids in the wine to be combined, the nanofiltration retentate and the distillation residue were mixed, water was added to reduce the concentration to 29% vol, activated carbon adsorption filtration was used to remove turbidity, and 10 L of pre-combined sample was prepared. The total acid of the pre-combined sample was 1.35 g / L, the total ester was 1.96 g / L, the acid-ester ratio was 1:1.45, the taste was slightly acidic, and the acid reduction treatment was appropriate. The target acid-ester ratio was set to 1:1.7. The total acid of the distillation residue was detected to be 2.85 g / L. According to the acid-base neutralization equivalent, the relevant treatment parameters for acid reduction were calculated by formulas 5, 6 and 7: the target total acid of the finished wine was 1.15 g / L, the minimum treatment residue volume was 103.7 L, and two neutralizing agents, MgO and Ca(OH)2, were added to reduce the acid by 50% and 50% respectively. The calculated amount of MgO added was 49.2 g and the amount of Ca(OH)2 added was 91.2 g.

[0043] (4) Based on the calculation results, take 110 L of the distillation residue and add 49.2 g MgO and 91.2 g Ca(OH)2 to neutralize and reduce acidity.

[0044] (5) The neutralized distillate is desalted by nanofiltration. When the acid-reduced permeate is collected to about 80 L, the retentate is gradually diluted with water and nanofiltration is continued to reduce the loss of ethanol and overall flavor. After treatment, the retentate is 20 L with an alcohol content of 5% vol. The ethanol loss caused by the high salt retentate is 0.2% of the original base wine.

[0045] (6) Mix the nanofiltration retentate, the undiluted distillate residue, and the diluted permeate, add water to reduce the alcohol content to 29% vol, with a total volume of about 1500 L, to obtain a cloudy wine.

[0046] (7) Activated carbon adsorption and filtration remove turbidity to obtain a clear wine.

[0047] (8) Blend and optimize the flavor to obtain the finished product of reduced alcohol content baijiu.

[0048] Comparative Example 2

[0049] The base liquor described in Example 2 was diluted to 29% vol by adding water, turbidity was removed by activated carbon adsorption and filtration, and the flavor was optimized by blending to obtain a comparison sample.

[0050] Table 5. Physicochemical and sensory comparison between Example 2 and Comparative Example 2 Example 2 1.18 1.95 1:1.65 41.8 1.136 Clear and transparent, with an elegant aged aroma and rich cellar fragrance, smooth and sweet, with a harmonious body, low in alcohol but not bland, and a long finish. Comparative Example 2 0.84 1.15 1:1.37 27.1 0.685 Clear and transparent, with a delicate cellar aroma and a pleasant grain fragrance. It has a smooth taste, slightly acidic, and watery, with a short aftertaste. As shown in Table 5, the 29% vol strong-aroma baijiu prepared using the distillation and de-alcoholization process and the nanofiltration desalting and acid reduction process had higher total acid and total ester contents than the traditionally diluted baijiu sample. The acid-ester ratio was more balanced, and the total acid-ester content and ethyl hexanoate content were 54% and 66% higher than the comparative sample, respectively. The example baijiu had a rich cellar aroma and an elegant and comfortable aged aroma, with a harmonious body that was not bland. In contrast, the comparative sample had a weak cellar aroma, a sour taste, and a watery flavor. Example 3: Preparation of 28% vol light-aroma baijiu using 60% vol base liquor

[0051] Light-aroma baijiu is mainly composed of ethyl acetate. The boiling point of ethyl acetate is close to that of ethanol. The ethyl acetate content is high in the first fraction of the distillate during the distillation and de-alcoholization process. Therefore, the proportion of the first fraction to be added back can be increased during the distillation operation. In addition, the content of higher alcohols will gradually increase in the later fraction of the distillate. Increasing the depth of de-alcoholization can reduce the content of higher alcohols in the liquor.

[0052] 1300 L of 28% vol light-aroma ultra-low-alcohol baijiu was prepared using 1000 L of 60% vol 5-year-old light-aroma base liquor, employing the aforementioned distillation and alcohol reduction process. Before base liquor treatment, based on the law of conservation of ethanol volume, relevant alcohol reduction parameters were calculated using equations 1, 2, 3, and 4: the ethanol removal volume was 236 L, and the alcohol content of the distillate was controlled at 92% vol, resulting in a distillate volume of 256.5 L. The alcohol content of the distillate residue (including the back-added fraction) was set at 25% vol. Referring to the table, the density of the 92% vol distillate at 20℃ is 0.822 kg / L, the density of the 25% vol distillate residue is 0.968 kg / L, and the density of the 60% vol nanofiltration permeate is 0.908 kg / L. Based on the parameters listed above, the theoretical volume of the nanofiltration permeate was 496.7 L, and the theoretical volume of the nanofiltration retentate was 503.3 L.

[0053] (1) The base wine was treated by nanofiltration (molecular weight cutoff 100 Da) and 503.3 L of retentate and 496.7 L of permeate were collected.

[0054] (2) The above permeate is distilled to control the distillation fraction to 92% vol. The first part of the fraction, which accounts for 15% of the permeate volume, i.e. 74.5 L, is collected for later use. The other part of the de-alcoholized fraction, which is not added back, is collected. After the distillation is completed, the aforementioned reserved fraction is added back to the distillation residue.

[0055] (3) According to the volume ratio of the two liquids in the wine to be combined, take nanofiltration retentate and distillation residue respectively, mix them, add water to reduce the concentration to 28% vol, remove turbidity by activated carbon adsorption filtration, and prepare 5 L of pre-combined sample. The total acid of the pre-combined sample is 1.04 g / L, the total ester is 1.87 g / L, the acid-ester ratio is 1:1.80, the acid-ester ratio is reasonable, the taste is comfortable, and no acid reduction treatment is required.

[0056] (4) Mix the nanofiltration retentate and the distillation residue, add water to reduce the concentration to 28% vol, with a total volume of about 1300 L, to obtain a cloudy wine.

[0057] (5) Activated carbon adsorption and filtration remove turbidity to obtain a clear wine.

[0058] (6) Blend and optimize the flavor to obtain the finished product of reduced alcohol content baijiu.

[0059] Comparative Example 3

[0060] The base liquor described in Example 3 was diluted to 28% vol by adding water, turbidity was removed by activated carbon adsorption and filtration, and the flavor was optimized by blending to obtain a comparison sample.

[0061] Table 6. Physicochemical and sensory comparison between Example 3 and Comparative Example 3 Example 3 1.04 1.90 1:1.83 38.9 1.068 Clear and transparent, with a pure and delicate fragrance, elegant and harmonious aroma, mellow and sweet, full-bodied, smooth and refreshing, and a long-lasting aftertaste. Comparative Example 3 0.58 1.17 1:2.02 23.0 0.613 Clear and transparent, with a pure and pleasant aroma, a smooth taste, a short aftertaste, and a faint finish. As shown in Table 6, the total ester content and ethyl acetate content of the 28% vol light-aroma baijiu prepared in this example are approximately 69% and 74% higher than those of the comparative example, respectively. The sensory evaluation results show that the aroma is pure, elegant, harmonious, mellow, and sweet; the comparative example has light-aroma characteristics, a smoother taste, but lower content of flavor components, shorter aftertaste, and weaker finish.

[0062] Example 4: Production of 39% vol Maotai-flavor Baijiu using 54% vol base liquor

[0063] In this embodiment, a diluted baijiu was prepared using a sauce-flavored base liquor, and neutralization and nanofiltration desalination were performed to reduce acidity based on the acidity and acid-ester ratio of the pre-combined sample.

[0064] 1000 L of 39% vol Maotai-flavor liquor was prepared from 1000 L of 54% vol 5-year-old Maotai-flavor base liquor. Before base liquor treatment, based on the conservation of ethanol volume, relevant alcohol reduction parameters were calculated with reference to Equations 1, 2, 3, and 4: the ethanol removal volume was 150 L, and the alcohol content of the distillate was controlled at 94% vol, so the volume of the distillate was 159.6 L; the alcohol content of the distillate residue (including the back-added fraction) was set to 30% vol. From the table, the density of the 94% vol distillate at 20℃ was 0.815 kg / L, the density of the 30% vol distillate residue was 0.962 kg / L, and the density of the 54% vol nanofiltration permeate was 0.922 kg / L. The calculated volume of the nanofiltration permeate was 433.5 L, and the volume of the nanofiltration retentate was 566.5 L.

[0065] (1) The base wine was circulated through nanofiltration (molecular weight cutoff 150 Da), and 566.5 L of retentate and 433.5 L of permeate were collected.

[0066] (2) The above permeate is distilled to control the distillate fraction at 94% vol. The first 5% of the permeate volume, i.e., 21.7 L, is collected for later use. The remaining 159.6 L of the dealcoholized fraction is collected and not added back. After the distillation is completed, the aforementioned reserved fraction is added back to the distillate residue.

[0067] (3) According to the volume ratio of the two liquids in the wine to be combined, the nanofiltration retentate and the distillation residue were mixed, water was added to reduce the concentration to 39% vol, and the turbidity was removed by freeze filtration. 5 L of pre-combined sample was prepared. The total acid of the pre-combined sample was 2.82 g / L, the total ester was 3.18 g / L, the acid-ester ratio was 1:1.13, the acid taste was prominent, and acid reduction treatment was required. The target acid-ester ratio was set to 1:1.5. The total acid of the distillation residue was detected to be 5.29 g / L. According to the acid-base neutralization equivalent, the relevant treatment parameters for acid reduction were calculated by formulas 5, 6 and 7: the target total acid of the finished wine was 2.12 g / L, the minimum treatment residue volume was 132.3 L, and two neutralizing agents, MgCO3 and Ca(OH)2, were added to reduce the acid by 30% and 70% respectively. The amount of MgCO3 added was 147 g and the amount of Ca(OH)2 added was 302.3 g.

[0068] (4) Based on the calculation results, take 150 L of distillation residue and add 147 g MgCO3 and 302.3 g Ca(OH)2 to neutralize and reduce acidity.

[0069] (5) The distillation residue after neutralization is desalted by nanofiltration. When the permeate (acid-reduced permeate) is collected to about 100 L, the retentate is gradually diluted with water and nanofiltration is continued. After treatment, the retentate is 25 L with an alcohol content of 6% vol. The high salt retentate causes an ethanol loss of 0.3% of the original base wine.

[0070] (6) Mix the nanofiltration retentate, the undiluted distillate, and the diluted permeate, add water to reduce the alcohol content to 39% vol, with a total volume of about 1000 L, to obtain a cloudy wine.

[0071] (7) The wine is frozen and filtered to remove turbidity, resulting in a clear wine.

[0072] (8) Blend and optimize the flavor to obtain the finished product of reduced alcohol content baijiu.

[0073] Comparative Example 4

[0074] The base liquor described in Example 4 was diluted to 39% vol by adding water, then frozen and filtered to remove turbidity, and blended to optimize the flavor, resulting in a comparison sample.

[0075] Table 7. Physicochemical and sensory comparisons between Example 4 and Comparative Example 4 Example 4 2.10 3.15 1:1.50 70.8 Slightly yellow and transparent, with distinct aromas of soy sauce and yeast, the fragrance is harmonious and lingers long in the empty glass. The body is mellow, full-bodied, and harmonious, with a long finish. Comparative Example 4 2.17 2.24 1:1.03 61.6 Clear and transparent, with a pronounced soy sauce aroma and a hint of yeast fragrance; the aroma lingers even after the glass is empty. It has a slightly sour taste upon first sip, followed by a sour and astringent aftertaste. As shown in Table 7, the total ester content of the 39% vol Maotai-flavor Baijiu prepared in this example is about 15% higher than that of the comparative example, with a total acidity of 2.10 g / L, a total ester content of 3.15 g / L, and an ester-ester ratio of 1:1.50. The sensory evaluation results show that the Baijiu has a mellow and harmonious body; the comparative example has a weaker Maotai-flavor and a more prominent acidity.

[0076] Example 5: Preparation of 45% vol Special Aroma Baijiu from 61% vol Special Aroma Base Liquor

[0077] The following examples employ a distillation-based de-alcoholization process. If the acid-ester ratio and sensory evaluation results of the pre-combined sample meet the requirements of this example, no acid reduction treatment is performed.

[0078] 1000 L of 45% vol special-aroma baijiu was prepared from 1000 L of 61% vol 6-year-old special-aroma base liquor using the aforementioned distillation and alcohol reduction process. Before base liquor treatment, based on the conservation of ethanol volume, relevant alcohol reduction parameters were calculated using Equations 1, 2, 3, and 4: the ethanol removal volume was 160 L, and the alcohol content of the distillate fraction was controlled at 92% vol, resulting in a distillate volume of 173.9 L. The alcohol content of the distillate residue (including the back-added fraction) was set at 35% vol. Referring to the table, the density of the 92% vol distillate fraction at 20℃ was 0.822 kg / L, the density of the 35% vol distillate residue was 0.956 kg / L, and the density of the 61% vol nanofiltration permeate was 0.907 kg / L. Therefore, the nanofiltration permeate volume was calculated to be 387.4 L, and the nanofiltration cutoff volume was 612.6 L.

[0079] (1) The base wine was circulated through nanofiltration (molecular weight cutoff 250 Da), and 387.4 L of permeate and 612.6 L of retentate were collected respectively.

[0080] (2) The above permeate is distilled and the distillate fraction is controlled at 92% vol. The first part of the permeate volume, which accounts for 10% of the volume, i.e. 38.7 L, is collected for later use. The dealcoholized fraction that is not added back is also collected, which is about 173.9 L. After the distillation is completed, the aforementioned reserved fraction is added back to the distillate residue.

[0081] (3) According to the volume ratio of the two liquids in the wine to be combined, the nanofiltration retentate and the distillation residue were mixed and diluted with water to 45% vol. 3 L of pre-combined sample was prepared. The turbidity was removed by activated carbon adsorption filtration. The total acid of the pre-combined sample was 1.55 g / L, the total ester was 3.24 g / L, and the acid-ester ratio was 1:2.09, which was reasonable. The sensory evaluation found that the acidity was suitable, so no acid reduction treatment was performed.

[0082] (4) Mix the nanofiltration retentate and the distillation residue, add water to reduce the concentration to 45% vol, with a total volume of about 1000 L, to obtain a cloudy wine.

[0083] (5) The wine is frozen and filtered to remove turbidity, resulting in a clear wine.

[0084] (6) Blend and optimize the flavor to obtain the finished product of reduced alcohol content baijiu.

[0085] Comparative Example 5

[0086] The base liquor described in Example 5 was diluted to 45% vol by adding water, then frozen and filtered to remove turbidity, and blended and optimized to obtain a control sample.

[0087] Table 8. Physicochemical and sensory comparison between Example 5 and Comparative Example 5 Example 5 1.55 2.98 1:1.92 59.7 Clear and transparent, with a delicate and pleasant aroma, a complex blend of aged, cellar, soy sauce, and rice notes. On the palate, it is mellow, sweet, and smooth, with a full and rounded body, harmonious flavors, and a long finish. Comparative Example 5 1.20 2.56 1:2.13 49.0 Clear and transparent, with a delicate and pleasant aroma, a complex fragrance of cellar and rice notes. On the palate, it is sweet and refreshing, with a smooth body and a long finish. As shown in Table 8, the total acid, total ester, and total acid and ester content of the 45% vol diluted baijiu prepared by the distillation and alcohol removal process are all higher than those prepared by the traditional water dilution method. It has an elegant aroma, a full body, prominent aged aroma characteristics, and a long aftertaste. In contrast, the flavor of the traditional water dilution baijiu is diluted, with a light aroma and a sweet taste.

[0088] The scope of protection of this invention is defined by the claims.

Claims

1. A process for reducing the alcohol content and acidity of baijiu (Chinese liquor), characterized in that, Includes the following steps: (1) Nanofiltration is performed on the base wine, and the nanofiltration retentate and nanofiltration permeate are collected separately; (2) Calculate the de-alcoholization treatment parameters according to the base liquor volume, base liquor alcohol content, target alcohol content and target liquor volume, based on the ethanol volume conservation principle; distill the nanofiltration permeate and collect the first fraction and the fraction used to remove ethanol, respectively. The volume of the first fraction accounts for 1% to 15% of the volume of the nanofiltration permeate; after the distillation is completed, add the first fraction back to the distillation residue. (3) Take the nanofiltration retentate and the distillation residue after adding the first distillate to prepare a pre-combined sample, conduct sensory evaluation and detect the total acid and total ester content, and determine whether to carry out acid reduction treatment based on the sensory evaluation results and the target acid-ester ratio; (4) When acid reduction is required, take part or all of the distillation residue, add one or more of MgO, Ca(OH)2, and MgCO3 for neutralization, and then perform nanofiltration desalination. Collect the acid-reduced permeate and the high-salt retentate separately. When acid reduction is not required, retain the distillation residue for mixing. (5) For wine that has undergone deacidification treatment, combine the nanofiltration retentate, deacidified permeate, and undeacidified distillate. If all distillate residues have undergone deacidification treatment, do not add undeacidified distillate residues. For wine that has not undergone deacidification treatment, combine the nanofiltration retentate and distillate residues. Add water to the target alcohol content to obtain the wine to be deturbided. (6) Filter to remove turbidity and obtain a clear wine; (7) Blend to obtain the finished product of reduced alcohol content liquor.

2. The method for reducing the alcohol content and acidity of baijiu according to claim 1, characterized in that, The nanofiltration process uses an organic solvent-resistant nanofiltration membrane with a molecular weight cutoff of 100–300 Da and a divalent salt removal rate of over 98%.

3. The method for reducing the alcohol content and acidity of baijiu according to claim 1, characterized in that, The alcohol content of the fraction used to remove ethanol is above 90% vol.

4. The method for reducing the alcohol content and acidity of baijiu according to claim 1, characterized in that, The pre-combined sample is sampled and mixed according to the volume ratio of nanofiltration retentate and distillation residue in the wine to be combined, water is added to the target alcohol content and filtered to remove turbidity, so as to prepare 1-10 L pre-combined sample.

5. The method for reducing the alcohol content and acidity of baijiu according to claim 1, characterized in that, The acid reduction treatment includes: a. Calculate the amount of neutralizing agent based on the total acidity of the pre-combined sample, the target total acidity, and the target volume of the liquor, according to the acid-base neutralization equivalent, and calculate the volume of the distillate to be treated based on the total acidity of the distillate. b. Take the distillation residue to be treated and neutralize it by adding one or more of food-grade MgO, Ca(OH)2, and MgCO3. c. Perform nanofiltration desalination on the neutralized distillation residue; after the volume of the collected desalted permeate reaches 50% to 80% of the initial volume of the distillation residue to be treated, gradually add water to dilute the high-salt retentate and continue nanofiltration until the alcohol content of the high-salt retentate is less than 10% vol and the volume is not greater than 20% of the initial volume of the distillation residue to be treated; collect the desalted permeate.

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