Method for removing baijiu mud odor and preparation method of high-quality baijiu

Abstract

The invention relates to the technical field of white spirit quality improvement, and discloses a method for removing mud odor of white spirit and a preparation method of high-quality white spirit, the method comprises the following steps: (1) carrying out membrane treatment on the white spirit to obtain penetrating fluid and retentate; (2) mixing the retentate with carboxyl modified activated carbon, performing static adsorption, and performing solid-liquid separation to obtain clear liquid; and (3) carrying out dynamic adsorption on the clear liquid through weakly alkaline anion resin. By adopting the method disclosed by the invention, directional removal of mud odors such as butyric acid and 4-methylphenol in the baijiu can be realized, meanwhile, original flavor substances of the baijiu are reserved to the greatest extent, and the content of butyric acid and the content of 4-methylphenol in the prepared high-quality baijiu can be respectively reduced to be lower than the odor threshold values of 111-231 mg / L and 1.33-1.55 mg / L by adopting the method disclosed by the invention; the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate and the like) is greater than or equal to 89%.

Description

Technical Field

[0001] This invention relates to the technical field of improving the quality of baijiu (Chinese liquor), specifically to a method for removing the muddy odor from baijiu and a method for preparing high-quality baijiu. Background Technology

[0002] Baijiu, a traditional Chinese distilled spirit, is influenced by a variety of trace components in terms of flavor and quality. Butyric acid (C4H8O2) and 4-methylphenol (C7H8O) are key off-odor substances that contribute to the earthy and leathery smells of the spirit, with thresholds as low as 111-231 mg / L and 1.33-1.55 mg / L, respectively. Even trace amounts can significantly affect sensory quality. However, existing removal technologies face three major bottlenecks: (1) Poor selectivity: Traditional activated carbon or resin adsorption lacks targeting, and key flavor substances such as esters (ethyl hexanoate, ethyl lactate) and pyrazines are lost simultaneously when removing odor substances; (2) Low efficiency: Butyric acid is difficult to be effectively retained by conventional membrane separation due to its small molecular weight and weak polarity. 4-Methylphenol has significantly reduced adsorption activity in ethanol environment. Ultrafiltration or nanofiltration membranes can remove large molecular impurities, but they cannot be used to separate low molecular weight butyric acid and 4-methylphenol. (3) Insufficient process compatibility: For example, CN118516206A uses a combination of "activated carbon + freeze filtration + resin adsorption", which can remove 4-methylphenol and 3-methylindole, but has high energy consumption (-15℃ freezing) and cannot effectively remove butyric acid; CN110317768A uses microorganisms such as lactic acid bacteria to degrade the 4-methylphenol content in baijiu, but the fermentation process is prone to introducing new impurities, and the treatment cycle is as long as 72 hours or more, which is not suitable for industrial continuous production. Summary of the Invention

[0003] The purpose of this invention is to overcome the technical problems of low removal rate of off-flavors in baijiu, large loss of flavor substances, and complex process in the existing technology, and to provide a method for removing the muddy odor of baijiu and a method for preparing high-quality baijiu. The method of this invention can efficiently remove the muddy odor (especially butyric acid and 4-methylphenol) in baijiu while minimizing the loss of the original flavor substances in baijiu.

[0004] To achieve the above objectives, the first aspect of the present invention provides a method for removing the muddy odor from baijiu (Chinese liquor), the method comprising the following steps: (1) The liquor is subjected to membrane treatment to obtain permeate and residual liquid; (2) The residual liquid is mixed with carboxyl-modified activated carbon and subjected to static adsorption, followed by solid-liquid separation to obtain a clear liquid; (3) The clear liquid is dynamically adsorbed by a weakly basic anion exchange resin.

[0005] A second aspect of the present invention provides a method for preparing baijiu (Chinese liquor), the method comprising mixing the permeate solution described in the present invention with the clear liquid after dynamic adsorption.

[0006] Through the above technical solution, the technical solution of the present invention achieves at least the following beneficial effects: the method of the present invention can achieve the targeted removal of earthy odors such as butyric acid and 4-methylphenol in baijiu, while retaining the original flavor substances of baijiu to the maximum extent. In the preferred embodiment of the present invention, the method of the present invention can reduce the content of butyric acid and 4-methylphenol in the prepared high-quality baijiu to below the odor thresholds of 111-231 mg / L and 1.33-1.55 mg / L, respectively, and the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate, etc.) is ≥90%. Detailed Implementation

[0007] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0008] The first aspect of this invention provides a method for removing the muddy odor from baijiu (Chinese liquor), the method comprising the following steps: (1) The liquor is subjected to membrane treatment to obtain permeate and residual liquid; (2) The residual liquid is mixed with carboxyl-modified activated carbon and subjected to static adsorption, followed by solid-liquid separation to obtain a clear liquid; (3) The clear liquid is dynamically adsorbed by a weakly basic anion exchange resin.

[0009] In this invention, the baijiu is made from grains as raw materials, through traditional solid-state fermentation, distillation, aging, and blending. No edible alcohol or flavoring substances not produced by baijiu fermentation are added. It is a strong-aroma baijiu with ethyl hexanoate as the main compound aroma and has an alcohol content of 65-75 vol.

[0010] According to some embodiments of the present invention, the conditions of the membrane treatment are such that the volume ratio of permeate to residual liquid is (1.5-3.5):1.

[0011] Preferably, the membrane treatment conditions are such that the volume ratio of permeate to residual liquid is (2-2.5):1.

[0012] In this invention, the membrane treatment includes an upstream section and a downstream section. Its working principle can be summarized in three stages: ① Adsorption and dissolution: One side of the membrane is in contact with the feed liquid. Based on chemical affinity, the membrane material preferentially "adsorbs" or "dissolves" the target substances (such as alcohols, esters, aldehydes, etc.); ② Diffusion and permeation: The adsorbed molecules diffuse from the high concentration side (feed liquid side) to the low concentration side (permeation side) of the membrane in the molecular-level channels or free volume inside the membrane. Since different molecules have different diffusion rates in the membrane, the target odor substances will pass through the membrane faster than water molecules, thereby achieving separation; ③ Vaporization and desorption: On the other side of the membrane (permeation side), by maintaining a vacuum or using purge gas, the permeated molecules are instantly vaporized and removed from the system.

[0013] Preferably, the conditions of the upstream section include: pressure of 0-0.1 MPa and temperature of 25-40°C; the conditions of the downstream section include: vacuum of 2000-6000 Pa and temperature of -70°C to -10°C.

[0014] Preferably, the conditions of the upstream and downstream sections also independently include: a membrane surface flow velocity of 0.1-0.6 m / s and a throughput of 0.5-3 L / (m³). 2 ·h).

[0015] In this invention, the membrane surface velocity (m / s) refers to the ratio of the flow rate of the feed liquid in the membrane tube (m³ / s) to the cross-sectional area of ​​the membrane tube (m²). Simply put, the membrane surface velocity is the speed at which the fluid flows on the membrane surface per unit time.

[0016] In this invention, the membrane treatment time also has a certain impact on the volume ratio of permeate to residual liquid. For example, under the same membrane treatment conditions, the difference in the volume ratio of permeate to residual liquid is related to the membrane treatment time. A longer treatment time consumes more resources (electricity, freezing, time, etc.), resulting in more permeate and less residual liquid. Preferably, the membrane treatment time is 12-48 hours. More preferably, the membrane treatment time is 20-30 hours.

[0017] In this invention, the membrane treatment time refers to the total duration of the upstream and downstream processes.

[0018] In this invention, the membrane material used in the membrane treatment consists of a support layer, an intermediate layer, and an activation layer.

[0019] In this invention, preferably, the support layer of the membrane material is composed of polyvinylidene fluoride, polypropylene, or polyester, which provides mechanical strength, withstands operating pressure, and ensures that the membrane module is not easily damaged. The thickness of the support layer is 100-200 μm. The intermediate layer is composed of cellulose acetate or polysulfone, which provides a smooth, stable, and highly porosity substrate for coating an extremely thin separation layer. It determines the flatness and long-term stability of the membrane. The activation layer is composed of polydimethylsiloxane or a polydimethylsiloxane-modified layer. It is the core functional layer of the membrane. The thickness of the activation layer is 0.5-10 μm.

[0020] In this invention, preferably, the membrane material is selected from PVE membrane, which is purchased from Nanjing Jiumo High-Tech Co., Ltd.

[0021] Preferably, the muddy odor comprises butyric acid and / or 4-methylphenol.

[0022] According to some embodiments of the present invention, preferably, in step (2), the surface carboxyl content of the carboxyl-modified activated carbon is 0.5-1.2 mmol / g.

[0023] Preferably, in step (2), the surface carboxyl content of the carboxyl-modified activated carbon is 1-1.2 mmol / g.

[0024] In this invention, the surface hydroxyl content of carboxyl-modified activated carbon is determined by measuring the acidic functional groups on the surface of activated carbon (Boehm titration method).

[0025] In this invention, preferably, the carboxyl-modified activated carbon is selected from citric acid-modified activated carbon.

[0026] In this invention, the preparation method of the citric acid modified activated carbon includes: adjusting the pH value of the activated carbon to neutral and drying it at 100-120℃ for 6-12 hours; mixing the dried activated carbon with a citric acid solution and stirring the reaction at 60-95℃ for 2-6 hours; filtering the reaction product and drying the resulting solid phase at 100-120℃ for 6-12 hours.

[0027] In this invention, preferably, the method for preparing citric acid modified activated carbon further includes adjusting the pH value of the solid phase obtained after filtration to neutral.

[0028] In this invention, there is no particular limitation on the method of adjusting the pH value of activated carbon or the solid phase obtained after filtration. For example, the method of adjusting the pH value of activated carbon or the solid phase obtained after filtration includes repeatedly rinsing the activated carbon or the solid phase obtained after filtration with deionized water so that the pH value of the activated carbon or the solid phase obtained after filtration is neutral.

[0029] Preferably, the activated carbon has an iodine value ≥1000mg / g and a specific surface area ≥1200m² / g.

[0030] In this invention, preferably, the activated carbon is selected from coconut shell charcoal.

[0031] Preferably, the citric acid solution has a citric acid concentration of 2-20 wt%.

[0032] In this invention, preferably, the mass ratio of activated carbon to citric acid solution is 1:(5-10).

[0033] According to some embodiments of the present invention, preferably, in step (2), the amount of modified activated carbon used is 0.1-2g based on the volume of 100mL of the permeate.

[0034] Preferably, in step (2), the amount of carboxyl-modified activated carbon used is 0.3-1g, based on the volume of 100mL of the permeate.

[0035] Preferably, in step (2), the conditions for static adsorption include: a temperature of 20-25°C and a time of 6-72h.

[0036] In this invention, in order to improve the adsorption effect of carboxyl-modified activated carbon on the muddy odor substances (especially butyric acid) in baijiu, preferably, in step (2), the method further includes pre-adsorption of the carboxyl-modified activated carbon before static adsorption.

[0037] Preferably, the pre-adsorption method includes soaking the carboxyl-modified activated carbon in an ethanol solution for 1-2 hours.

[0038] Preferably, the ethanol concentration in the ethanol solution is 50-95 wt%.

[0039] In this invention, preferably, in step (2), the solid-liquid separation method is filtration.

[0040] Preferably, the filtration method includes filtering the adsorbed clear liquid in a diatomaceous earth filter.

[0041] According to some embodiments of the present invention, in step (3), the weakly basic anion exchange resin is selected from styrene-based weakly basic anion exchange resins and / or diethylene-based weakly basic anion exchange resins.

[0042] In this invention, the styrene-based weakly basic anion exchange resin was purchased from Xi'an Lanxiao Technology New Materials Co., Ltd., with the product model LX-718B; the diethylene-based adsorption resin was sourced from Jiangsu Suqing Water Treatment Engineering Group Co., Ltd., with the product model DA201-HP.

[0043] In this invention, the weakly basic anion exchange resin refers to a resin column filled with resin, preferably, The filling mass of the weakly basic anion exchange resin is 5-10 wt% of the mass of the permeate; the filling height-to-diameter ratio of the weakly basic anion exchange resin is (3-5):1.

[0044] In this invention, the "filling height-to-diameter ratio" of the resin in the weakly basic anion exchange resin refers to the ratio of the filling height of the resin in the resin column to the diameter of the resin column, and the unit can be cm / cm or m / m.

[0045] Preferably, the conditions for dynamic adsorption include: inlet temperature of 20-30℃, injection flow rate of 1.5-3 BV / h, and time of 3-10h.

[0046] Preferably, the dynamic adsorption time is 5-6 hours.

[0047] In this invention, in order to improve the adsorption effect of the weakly basic anion exchange resin on 4-methylphenol in liquor, preferably, in step (3), the method further includes pre-treating the weakly basic anion exchange resin before dynamic adsorption.

[0048] Preferably, the pretreatment method includes soaking the weakly basic anion exchange resin in an ethanol solution for 12-24 hours.

[0049] Preferably, the ethanol concentration in the ethanol solution is 70-95 wt%.

[0050] A second aspect of the present invention provides a method for preparing baijiu (Chinese liquor), the method comprising mixing the permeate solution described in the present invention and the clear liquid after dynamic adsorption.

[0051] Preferably, the volume ratio of the permeate to the clear liquid after dynamic adsorption is (1.5-4):1.

[0052] According to a particularly preferred embodiment of the present invention, a method for preparing high-quality baijiu (Chinese liquor) is provided, the method comprising the following steps: (1) The liquor was passed through a PVE membrane to obtain permeate and residual liquid; The volume ratio of the permeate to the residual liquid is (2-2.5):1; The membrane treatment includes an upstream section and a downstream section; the conditions of the upstream section include: pressure of 0-0.1 MPa and temperature of 30-40°C; the conditions of the downstream section include: vacuum of 4000-6000 Pa and temperature of -20°C to -10°C. The membrane surface flow rate during the membrane treatment is 0.2-0.6 m / s, and the throughput is 2-3 L / (m³).2 ·h); The membrane treatment time is 20-25 hours. (2) The citric acid modified activated carbon (the surface carboxyl content of the citric acid modified activated carbon is 1-1.2 mmol / g) is soaked in an ethanol solution with a mass concentration of 70-80 wt% for 1-2 h for pre-adsorption; then the leachate is mixed with the pre-adsorbed carboxyl modified activated carbon and statically adsorbed at 20-25℃ for 24-36 h, and then solid-liquid separation is performed (filtered in a diatomaceous earth filter) to obtain a clear liquid; Based on the volume of 100 mL of the permeate, the amount of carboxyl-modified activated carbon used is 0.3-0.6 g. (3) Soak the styrene-based weakly basic anion exchange resin in an ethanol solution with a mass concentration of 80-95wt% for 15-24h for pretreatment; then pass the clear liquid through the styrene-based weakly basic anion exchange resin at a flow rate of 1.5-2BV / h, with an inlet temperature of 25-30℃, and perform dynamic adsorption for 5-6h to obtain the clear liquid after dynamic adsorption. The resin loading amount in the styrene-based weakly basic anion exchange resin is 8-10 wt% of the permeate volume. The height-to-diameter ratio of the resin in the styrene-based weakly basic anion exchange resin is (3-5):1. (4) Mix the permeate from step (1) and the clear liquid after dynamic adsorption at a volume ratio of (2-2.5):1 to obtain high-quality liquor.

[0053] The present invention will be described in detail below through embodiments.

[0054] The baijiu is a low-end, rich-aroma type, with an alcohol content of 70 vol%, butyric acid of 498.46 mg / L, 4-methylphenol of 3.03 mg / L, total acid of 1.3 g / L, and total ester content of 4.8 g / L.

[0055] The PVE membrane was purchased from Nanjing JiuMo High-Tech Co., Ltd., and the product model is JiuMo-PVE-01 series.

[0056] The preparation method of citric acid modified activated carbon includes: washing coconut shell carbon with deionized water until the pH value is neutral, and drying at 105℃ for 8 hours; soaking the dried activated carbon in a mixture of 4wt% citric acid solution for 24 hours (the mass ratio of activated carbon to citric acid solution is 1:10), stirring at a constant temperature of 60℃ for 6 hours; filtering the reaction product, washing the obtained solid phase with deionized water until the pH value is neutral, and drying at 105℃ for 8 hours.

[0057] The preparation method of hydrogen peroxide modified activated carbon includes: washing coconut shell carbon with deionized water until neutral, drying at 105℃ for 12h to remove impurities; then immersing the dried coconut shell carbon in a 10wt% hydrogen peroxide solution (the mass ratio of coconut shell carbon to hydrogen peroxide solution is 1:10), stirring and reacting at 70℃ for 5h; then filtering the reaction product, repeatedly rinsing the obtained solid phase with deionized water until the pH of the washing solution is close to neutral, and then drying at 105℃ for 12h.

[0058] The coconut shell charcoal was purchased from Fujian Yuanli Activated Carbon Co., Ltd. The iodine value of the coconut shell charcoal is ≥1000mg / g, and the specific surface area is ≥1200m². 2 / g.

[0059] The styrene-based weakly basic anion exchange resin was purchased from Xi'an Lanxiao Technology New Materials Co., Ltd., product model LX-718B.

[0060] Example 1 (1) The liquor was passed through a PVE membrane to obtain permeate and residual liquid; The volume ratio of the permeate to the residual liquid is 7:3; The membrane treatment includes an upstream section and a downstream section; the conditions of the upstream section include a pressure of 0.1 MPa and a temperature of 40°C; the conditions of the downstream section include a vacuum of 6000 Pa and a temperature of -10°C. The membrane surface flow rate during the membrane treatment is 0.6 m / s, and the processing capacity is 2 L / (m³). 2 ·h); The membrane treatment time is 22 hours. (2) The citric acid modified activated carbon (the surface carboxyl content of the citric acid modified activated carbon is 1.2 mmol / g) was soaked in an ethanol solution with a mass concentration of 70 wt% for 2 h for pre-adsorption; then the leachate was mixed with the pre-adsorbed carboxyl modified activated carbon and statically adsorbed at 25 °C for 24 h, and then solid-liquid separation was performed (filtered in a diatomaceous earth filter) to obtain a clear liquid; Based on the volume of 100 mL of the permeate, the amount of carboxyl-modified activated carbon used is 0.3 g. (3) The styrene-based weak base anion exchange resin was soaked in an ethanol solution with a mass concentration of 95wt% for 24h for pretreatment; then the clear liquid was passed through the styrene-based weak base anion exchange resin at a flow rate of 1.5BV / h, with the feed temperature at 30℃, and dynamically adsorbed for 6h to obtain the clear liquid after dynamic adsorption. The resin loading amount in the styrene-based weakly basic anion exchange resin is 8 wt% of the permeate volume. The height-to-diameter ratio of the resin in the styrene-based weakly basic anion exchange resin is 5:1. (4) Mix the permeate from step (1) and the clear liquid after dynamic adsorption at a volume ratio of 7:3 to obtain high-quality liquor; The high-quality baijiu prepared according to the method of Example 1 has a butyric acid content of 70.2 mg / L, a 4-methylphenol content of 0.19 mg / L, and a total acid and total ester retention rate of 92%. The high-quality baijiu of Example 1 has "disappeared earthy odor and prominent cellar aroma".

[0061] Example 2 (1) The liquor was passed through a PVE membrane to obtain permeate and residual liquid; The volume ratio of the permeate to the residual liquid is 7:3; The membrane treatment includes an upstream section and a downstream section; the conditions of the upstream section include a pressure of 0.1 MPa and a temperature of 40°C; the conditions of the downstream section include a vacuum of 6000 Pa and a temperature of -10°C. The membrane surface flow rate during the membrane treatment is 0.6 m / s, and the processing capacity is 2 L / (m³). 2 ·h); The membrane treatment time is 22 hours. (2) The citric acid modified activated carbon (the surface carboxyl content of the citric acid modified activated carbon is 1.2 mmol / g) was soaked in an ethanol solution with a mass concentration of 70 wt% for 2 h for pre-adsorption; then the leachate was mixed with the pre-adsorbed carboxyl modified activated carbon and statically adsorbed at 25 °C for 24 h, and then solid-liquid separation was performed (filtered in a diatomaceous earth filter) to obtain a clear liquid; Based on the volume of 100 mL of the permeate, the amount of carboxyl-modified activated carbon used is 0.3 g. (3) Soak the styrene-based weak base anion exchange resin in an ethanol solution with a mass concentration of 95wt% for 24h for pre-adsorption; then pass the clear liquid through the styrene-based weak base anion exchange resin at a flow rate of 2BV / h, with the feed temperature at 30℃, and perform dynamic adsorption for 5h to obtain the clear liquid after dynamic adsorption. The amount of the styrene-based weakly basic anion exchange resin is 8 wt% of the volume of the osmotic liquid. The height-to-diameter ratio of the resin in the styrene-based weakly basic anion exchange resin is 5:1. (4) Mix the permeate from step (1) and the clear liquid after dynamic adsorption at a volume ratio of 7:3 to obtain high-quality liquor; The high-quality baijiu prepared according to the method of Example 1 has a butyric acid content of 101.4 mg / L and a 4-methylphenol content of 0.18 mg / L. The high-quality baijiu of Example 2 has "disappeared earthy odor and prominent cellar aroma".

[0062] Example 3 The method of Example 1 is the same as that of Example 1, except that in step (2), the amount of carboxyl-modified activated carbon is 0.1g based on the volume of 100mL of the permeate. The other steps and conditions are the same as those of Example 1.

[0063] Example 4 The method of Example 1 differs in that, in step (1), the membrane filtration conditions are such that the volume ratio of permeate to residual liquid is 3:1. Specifically, in step (1), the conditions of the upstream section include: pressure of 0.1 MPa and temperature of 40°C; the conditions of the downstream section include: vacuum of 6000 Pa and temperature of -10°C; the membrane treatment time is 48 h; and the other steps and conditions are consistent with those of Example 1.

[0064] Example 5 The method of Example 1 is different in that, in step (2), the surface carboxyl content of the citric acid modified activated carbon is 0.8 mmol / g. Specifically, the preparation method of citric acid modified activated carbon includes: washing coconut shell carbon with deionized water until neutral, drying at 105°C for 12 h to remove impurities; then soaking the dried coconut shell activated carbon in a 4% citric acid solution, adding it at a solid-liquid ratio of 1:10 (e.g., 10g coconut shell carbon + 100mL citric acid solution), and allowing it to stand at 30°C for 24 h. Other steps and conditions are consistent with those of Example 1.

[0065] Example 6 The method of Example 1 differs in that, in step (1), the membrane filtration conditions are such that the volume ratio of permeate to residual liquid is 6:4. Specifically, in step (1), the conditions of the upstream section include: a pressure of 0.1 MPa and a temperature of 40°C; the conditions of the downstream section include: a vacuum of 6000 Pa and a temperature of -10°C; the membrane treatment time is 17 h; and the other steps and conditions are consistent with those of Example 1.

[0066] Comparative Example 1 The method is the same as in Example 1, except that in step (2), the citric acid-modified activated carbon is replaced with hydrogen peroxide-modified activated carbon. Specifically, the preparation method of hydrogen peroxide-modified activated carbon includes: washing coconut shell carbon with deionized water until neutral, drying at 105°C for 12 hours to remove impurities; then adding the dried activated carbon to a 10wt% hydrogen peroxide solution at a solid-liquid ratio of 1:10 (e.g., 10g coconut shell carbon + 100mL hydrogen peroxide solution), stirring and reacting at 70°C for 7 hours; then rinsing repeatedly with deionized water until the pH of the washing solution is close to neutral, and drying in an oven at 105°C for 12 hours. The other steps and conditions are the same as in Example 1.

[0067] Comparative Example 2 The method of Example 1 is the same, except that in step (2), the citric acid modified activated carbon is replaced with nitric acid modified activated carbon. Specifically, the preparation method of nitric acid modified activated carbon includes: washing coconut shell carbon with deionized water until neutral, drying at 105°C for 12 hours to remove impurities; mixing the dried coconut shell carbon and nitric acid solution (mass concentration of 30wt%) at a solid-liquid ratio of 1:10 (e.g., 10g coconut shell carbon + 100mL nitric acid solution), heating in a water bath at 80°C for 5 hours; filtering the reaction product, rinsing the obtained solid phase repeatedly with deionized water until the pH of the washing liquid is close to neutral, and drying at 105°C for 12 hours; the other steps and conditions are the same as in Example 1.

[0068] Comparative Example 3 The method of Example 1 is the same as that of Example 1, except that in step (2), the citric acid modified activated carbon is replaced with molecular sieve (the molecular sieve is purchased from Dalian Haixin Chemical Co., Ltd., and the product model is 4A molecular sieve). The other steps and conditions are the same as those of Example 1.

[0069] Comparative Example 4 The method of Example 1 is the same as that of Example 1, except that in step (3), the styrene-based weakly basic anion exchange resin is replaced with diethylene-based adsorption resin (purchased from Jiangsu Suqing Water Treatment Engineering Group Co., Ltd., product model DA201-HP), and the other steps and conditions are the same as those of Example 1.

[0070] Comparative Example 5 The liquor was mixed with activated carbon (unmodified coconut shell activated carbon) and statically adsorbed at 25°C for 24 hours. Then, solid-liquid separation was performed (filtered in a diatomaceous earth filter) to obtain a clear liquid. The amount of activated carbon used was 0.3g based on the volume of 100mL of liquor.

[0071] Comparative Example 6 (1) Mix the liquor with activated carbon (unmodified coconut shell activated carbon) and perform static adsorption at 25°C for 24 hours to obtain a mixed solution. The amount of activated carbon used is 0.3g based on the volume of 100mL liquor. (2) The mixture was frozen at -5°C for 2 hours, and then solid-liquid separation was performed (filtered in a diatomaceous earth filter) to obtain a clear liquid; (3) The styrene-based weak base anion exchange resin was soaked in an ethanol solution with a mass concentration of 95wt% for 24h for pretreatment; then the clear liquid was passed through the styrene-based weak base anion exchange resin at a flow rate of 1.5BV / h, the inlet temperature was 30℃, and dynamic adsorption was carried out for 6h to obtain high-quality liquor.

[0072] The amount of resin in the weakly basic anion exchange resin is 8% of the volume of the liquor.

[0073] Test case The contents of butyric acid, 4-methylphenol, total acid and total ester in the high-quality baijiu prepared in the above examples and comparative examples were determined, and the removal rates of butyric acid, 4-methylphenol and total acid and total ester in the baijiu were calculated. Sensory evaluation of the high-quality baijiu in examples and comparative example 1 was also performed, and the results are shown in Table 1.

[0074] The removal rate (%) of butyric acid in baijiu is calculated as follows: 100% × (butyric acid content in baijiu - butyric acid content in high-quality baijiu) / butyric acid content in baijiu.

[0075] The removal rate (%) of 4-methylphenol in baijiu is calculated as follows: 100% × (content of 4-methylphenol in baijiu - content of 4-methylphenol in high-quality baijiu) / content of 4-methylphenol in baijiu.

[0076] The retention rate (%) of total acid and total ester in baijiu = 100% × (total content of total acid and total ester in baijiu - total content of total acid and total ester in high-quality baijiu) / total content of total acid and total ester in baijiu. The total acid and total ester are calculated based on the total content of ethyl hexanoate and ethyl acetate.

[0077] In this invention, the contents of butyric acid, 4-methylphenol, total acid and total ester in baijiu were determined by gas chromatography-mass spectrometry (GC-MS).

[0078] The sensory evaluation method for high-quality baijiu includes: grading and scoring by 10 or more national-level wine tasters, with the sensory evaluation scores expressed as the average value.

[0079] Table 1

[0080] Note: In Table 1, poor coordination of high-quality baijiu mainly refers to the balance and integration of taste, which is a quality defect. It has an off-flavor, weak and unfulfilling aroma. In terms of taste, it is strong and irritating, unbalanced in sweet, sour and bitter, and disconnected in the top, middle and bottom tastes. In terms of overall style, it is watery, thin and lacks mellowness and fullness. Weak main aroma focuses on the typicality and intensity of aroma, which is a style defect. For the rich aroma type, a weak main aroma means that the cellar aroma is not prominent when smelling, the aroma of ethyl hexanoate and ethyl acetate is weak, the aroma is weak, lacks a core structure, and the aroma persistence is poor.

[0081] As shown in Table 1, comparing Examples 1-2 with Examples 3-6 of this application, it can be seen that the high-quality liquor prepared using the preferred embodiments of the present invention can reduce the content of butyric acid and 4-methylphenol in the prepared high-quality liquor to below the odor thresholds of 111-231 mg / L and 1.33-1.55 mg / L, respectively, and the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate, etc.) is ≥89%.

[0082] Compared with the examples, Comparative Examples 1 and 2 replaced citric acid-modified activated carbon with hydrogen peroxide-modified activated carbon and nitric acid-modified activated carbon, respectively, resulting in a decrease in the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate, etc.) in the prepared high-quality baijiu; Comparative Example 3 replaced citric acid-modified activated carbon with molecular sieves, resulting in an increase in the content of 4-methylphenol and a decrease in the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate, etc.) in the prepared high-quality baijiu; Comparative Example 4 replaced styrene-based weakly basic anion exchange resin with diethylene-based adsorption resin. The resin caused the high-quality baijiu to have a prominent sour and astringent taste and poor harmony. In Comparative Example 5, baijiu was mixed with unmodified coconut shell activated carbon, which resulted in an increase in the content of 4-methylphenol in the high-quality baijiu and a slight decrease in the retention rate of key flavor substances (ethyl hexanoate, ethyl lactate, etc.), and the high-quality baijiu had a slightly off-flavor. Comparative Example 6 used a combination of "activated carbon + freeze filtration + resin adsorption", which could remove 4-methylphenol from the baijiu, but could not effectively remove butyric acid, and had high energy consumption. The high-quality baijiu produced lacked aroma and had a slightly sour taste.

[0083] In summary, the method of this invention can effectively remove the earthy odor (especially butyric acid and 4-methylphenol) from baijiu while minimizing the loss of the original flavor substances in the baijiu.

[0084] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for removing the muddy odor from baijiu (Chinese liquor), characterized in that, The method includes the following steps: (1) The liquor is subjected to membrane treatment to obtain permeate and residual liquid; (2) The residual liquid is mixed with carboxyl-modified activated carbon for static adsorption, and then solid-liquid separation is performed to obtain a clear liquid; (3) The clear liquid is dynamically adsorbed by a weakly basic anion exchange resin.

2. The method according to claim 1, wherein, The membrane treatment conditions are such that the volume ratio of permeate to residual liquid is (1.5-3.5):1, preferably (2-2.5):1; Preferably, the membrane treatment includes an upstream section and a downstream section; More preferably, the conditions of the upstream section include: pressure of 0-0.1 MPa and temperature of 25-40°C; the conditions of the downstream section include: vacuum of 2000-6000 Pa and temperature of -70°C to -10°C. More preferably, the conditions of the upstream and downstream sections also independently include: a membrane surface flow velocity of 0.1-0.6 m / s and a throughput of 0.5-3 L / (m³). 2 ·h).

3. The method according to claim 2, wherein, The muddy odor originates from butyric acid and / or 4-methylphenol.

4. The method according to claim 1, wherein, In step (2), the surface carboxyl content of the carboxyl-modified activated carbon is 0.5-1.2 mmol / g, preferably 1-1.2 mmol / g; Preferably, the carboxyl-modified activated carbon is selected from citric acid-modified activated carbon.

5. The method according to claim 4, wherein, The method for preparing citric acid modified activated carbon includes: adjusting the pH value of the activated carbon to neutral and drying it at 100-120℃ for 6-12 hours; mixing the dried activated carbon with a citric acid solution and stirring the reaction at 60-95℃ for 2-6 hours; filtering the reaction product and drying the resulting solid phase at 100-120℃ for 6-12 hours. Preferably, the activated carbon has an iodine value ≥1000 mg / g and a specific surface area ≥1200 m². 2 / g; Preferably, the citric acid solution has a citric acid concentration of 2-20 wt%.

6. The method according to any one of claims 1-4, wherein, In step (2), based on the volume of 100 mL of the permeate, the amount of carboxyl-modified activated carbon used is 0.1-2 g, preferably 0.3-1 g; Preferably, in step (2), the conditions for static adsorption include: a temperature of 20-25°C and a time of 6-72 hours; Preferably, in step (2), the method further includes pre-adsorbing the carboxyl-modified activated carbon before static adsorption; Preferably, the pre-adsorption method includes soaking the carboxyl-modified activated carbon in an ethanol solution for 1-2 hours; Preferably, the ethanol concentration in the ethanol solution is 50-95 wt%.

7. The method according to any one of claims 1-6, wherein, In step (3), the weakly basic anion exchange resin is a styrene-based weakly basic anion exchange resin and / or a diethylene-based weakly basic anion exchange resin. Preferably, the filling mass of the weakly basic anion exchange resin is 5-10 wt% of the mass of the permeate; the filling height-to-diameter ratio of the weakly basic anion exchange resin is (3-5):

1. Preferably, the conditions for dynamic adsorption include: inlet temperature of 20-30℃, injection flow rate of 1.5-3 BV / h, and time of 3-10h.

8. The method according to any one of claims 1-7, wherein, In step (3), the method further includes pretreating the weakly basic anion exchange resin before dynamic adsorption. Preferably, the pretreatment method includes soaking the weakly basic anion exchange resin in an ethanol solution for 12-24 hours; Preferably, the ethanol concentration in the ethanol solution is 70-95 wt%.

9. A method for preparing baijiu (Chinese white liquor), characterized in that, The method includes mixing the permeate as described in any one of claims 1-8 with the clear liquid after dynamic adsorption.

10. The method according to claim 9, wherein, The volume ratio of the permeate to the clear liquid after dynamic adsorption is (1.5-4):1.

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