A solid state fermentation liquor-making method for reducing content of higher alcohols

Abstract

The present application relates to the field of liquor brewing, and particularly to a solid fermentation liquor brewing method for reducing the content of higher alcohols; the method constructs a mechanism for targeted inhibition of isobutanol, isoamyl alcohol and n-propyl alcohol and promotion of the generation of ethyl hexanoate; accurate quantification and comparison by gas chromatography-mass spectrometry show that the core of the method is to significantly reduce higher alcohols and improve key aroma substances; the method of the present application blocks the synthesis of higher alcohols without changing the proportion of traditional flavor substances of liquor, guarantees the liquor yield, reduces the nervous stimulation after drinking, and improves the metabolic clearance rate of ethanol in the body.

Description

Technical Field

[0001] This invention relates to the field of baijiu brewing and microbial fermentation regulation technology, specifically a solid-state fermentation baijiu brewing method for reducing the content of higher alcohols. Background Technology

[0002] In the solid-state fermentation baijiu brewing system, under stress conditions of high temperature, lack of oxygen or unbalanced nitrogen source nutrition, brewing yeast is prone to excessive synthesis of higher alcohols such as isobutanol, isoamyl alcohol and n-propanol through the Ehrlich pathway and Harris pathway. When the content of higher alcohols exceeds the industry's conventional standards, it will cause the liquor to have a bitter taste and cause physiological discomfort after drinking.

[0003] Existing alcohol reduction technologies have the following technical defects: physical cooling reduces the overall metabolic activity of microorganisms, leading to incomplete fermentation and a decrease in alcohol yield; reducing the amount of yeast inoculated results in insufficient fermentation power and a lack of aroma production; the physical adsorption in the later stage lacks selectivity, and a large amount of key aroma substances such as ethyl hexanoate are adsorbed when removing higher alcohols, destroying the typical flavor components of baijiu; it is necessary to achieve targeted inhibition of higher alcohols and simultaneous enhancement of ester substances while maintaining the macroscopic process of traditional solid-state fermentation. Summary of the Invention

[0004] The purpose of this invention is to provide a solid-state fermentation method for reducing higher alcohols in baijiu (Chinese liquor) based on functionalized fermentation control materials. This method aims to address the problems of existing alcohol reduction techniques, which often result in insufficient fermentation kinetics and aroma production, or damage to the proportions of typical flavor compounds, making it difficult to achieve targeted inhibition of higher alcohols and simultaneous enhancement of ester compounds without altering traditional macroscopic processes. Specifically, the technical solution of this invention is as follows:

[0005] A method for brewing baijiu using solid-state fermentation to reduce the content of higher alcohols includes the following steps:

[0006] S1, Raw material processing: The brewing grain raw materials are crushed, moistened, steamed, and then cooled and maintained at 20°C. At 25℃, the cooled brewing grain raw materials were obtained;

[0007] S2, Combination of fermentation agent and regulating material: Daqu (a type of starter culture) is added to the cooled brewing grain raw material and mixed, while functional fermentation regulating material is added simultaneously to obtain fermented mash. The amount of functional fermentation regulating material added is 0.05% of the total mass of the fermented mash. 0.15%;

[0008] S3, Solid-state fermentation: The mash is placed in a fermentation pit for solid-state fermentation; in the early stage of fermentation, the outer shell of the functional fermentation control material swells and exudes polyphenolic substances; in the middle and late stages of fermentation, as the pH value of the mash decreases and the ethanol concentration increases, the outer shell of the functional fermentation control material undergoes deep swelling, which increases the permeability of the cross-linked network. Its core skeleton, which is composed of short-chain fatty acids grafted with microporous starch, breaks down under acidic conditions and the combined action of endogenous esterification enzymes in the mash system, releasing short-chain fatty acids, which combine with ethanol in the system and are converted in situ into corresponding ethyl ester flavor substances;

[0009] S4, Distillation: After fermentation, the fermented mash is removed from the cellar and distilled in a still, and the liquor is separated in stages to obtain a base liquor with low content of higher alcohols.

[0010] As a further preferred embodiment of the present invention, the preparation method of the functionalized fermentation regulating material includes the following steps:

[0011] Step (1) Extraction and enzymatic hydrolysis: Ultrasonic-assisted extraction with a volume fraction of 50% was used. Polyphenols were extracted from brewing byproducts using an 80% ethanol aqueous solution to obtain a polyphenol extract. β-glucosidase was added to the polyphenol extract for isothermal enzymatic hydrolysis to cleave glycosidic bonds and expose free phenolic hydroxyl groups. The enzyme was then inactivated and the extract was concentrated to obtain an active polyphenol solution.

[0012] Step (2) Esterification Grafting: Microporous starch is dispersed in purified water to form a starch emulsion. Food-grade alkali solution is added dropwise to adjust and maintain the pH of the system at a weakly alkaline level. The mass of the microporous starch is 30% of the total mass of the microporous starch added under constant stirring. A mixture of 50% hexanoic anhydride and butyric anhydride, wherein the mass ratio of hexanoic anhydride to butyric anhydride is 1:1. 3:1, at a temperature of 30 Esterification reaction was carried out at 50℃ 1 3h; after the reaction is complete, neutralize to neutral with food-grade acid, and then wash with water, dehydrate with anhydrous ethanol and vacuum dry to obtain short-chain fatty acid grafted microporous starch with hexanoyl and butyryl groups.

[0013] Step (3) Vacuum impregnation and assembly: Dissolve the active polyphenol solution in a solution with a volume fraction of 40%. In a 60% ethanol aqueous solution, the short-chain fatty acid-grafted microporous starch was added and mixed to obtain a mixed system. The mixed system was placed in a vacuum vessel, evacuated, and maintained for 30 minutes. Then, the vacuum was broken to force the active polyphenol solution into the micropores of the short-chain fatty acid-grafted microporous starch. The solvent was removed by evaporation under reduced pressure at 40°C to obtain the supported product.

[0014] Step (4) Formation of functionalized fermentation control material: The loaded product is uniformly dispersed in a water-soluble chitosan aqueous solution, and 0.1% of the mass of the water-soluble chitosan aqueous solution is added. 0.5% crosslinking agent genipin, at a temperature of 25°C Mild cross-linking pre-curing was performed at 40℃ 1 After 2 hours, the functionalized fermentation control material with a core-shell structure was obtained by spray drying.

[0015] Preferably, in step (1), the brewing byproduct is sorghum husk or grape seeds.

[0016] Preferably, in step (1), the isothermal enzymatic hydrolysis process conditions are: enzymatic hydrolysis temperature of 45°C. 50℃, pH value is 4.8.

[0017] Preferably, in step (2), the mass concentration of the starch milk is 30%. 40%, the food-grade alkali solution has a mass fraction of 5%. A 10% sodium hydroxide solution, the weakly alkaline pH being 8.0. 9.0.

[0018] Preferably, in step (3), the vacuuming process conditions are: vacuuming to an absolute pressure of 0.02 MPa and maintaining it for 30 minutes.

[0019] Preferably, in step (4), the mass concentration of the water-soluble chitosan aqueous solution is 3%. 5%.

[0020] Preferably, in step (4), the spray drying process conditions are: inlet air temperature of 140°C and outlet air temperature of 75°C.

[0021] Preferably, in step S3, the temperature control process for solid-state fermentation is as follows: after the first [stage / period] in the fermentation pit... The temperature inside the cellar was controlled at 26℃ for 7 days, and on the 8th day... The temperature was controlled at 31℃ on day 25, and on the 26th... The temperature naturally dropped to 28℃ after 60 days.

[0022] Preferably, in step S3, after the fermented mash is placed in the cellar... After 5 days, the outer shell of the functionalized fermentation control material swells and exudes polyphenolic substances; the fermented mash is then placed in the fermentation pit for 10 days. After 15 days, the pH of the mash decreased to 3.2. Within the 4.0 range and with the accumulation of ethanol concentration, the outer shell of the functionalized fermentation control material undergoes deep swelling, increasing the permeability of the cross-linked network. Under acidic conditions and with the combined action of endogenous esterifying enzymes in the mash system, the hexanoyl and butyryl groups grafted into the core skeleton break down and release hexanoic acid and butyryl acid, which then combine with ethanol in the system to convert into ethyl hexanoate and ethyl butyrylate.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. The method of the present invention combines a core-shell structured functional fermentation control material with the fermentation agent. In the early stage of fermentation, the outer shell of the material swells and exudes polyphenols, which effectively blocks the synthesis of higher alcohols, and finally obtains a baijiu base liquor with low higher alcohol content.

[0025] 2. In the middle and late stages of fermentation, as the pH of the mash decreases and the ethanol concentration increases, the outer shell of the functionalized fermentation control material undergoes deep swelling, which increases the permeability of the cross-linked network. Under the combined action of acidic conditions and endogenous esterification enzymes in the mash system, its core skeleton breaks down, releasing short-chain fatty acids, which combine with ethanol in the system and are converted in situ into corresponding ethyl ester flavor substances. This achieves targeted inhibition of higher alcohols and simultaneous enhancement of key aroma esters. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment provides a solid-state fermentation method for reducing higher alcohols in baijiu based on functionalized fermentation control materials. The specific operation is as follows:

[0029] S1. Raw material processing: Take 100kg of red sorghum, crush it until the mass fraction passing through a 20-mesh sieve is 85%, add 55kg of water to moisten the grain for 10 hours, steam under normal pressure for 45 minutes, remove from the steamer and keep at 22℃ to obtain the cooled brewing grain raw material; the moisture content of the cooked grain is controlled at 59%;

[0030] S2. Preparation of functionalized fermentation regulation materials:

[0031] Step 1: Extraction and Enzymatic Hydrolysis: Take 10 kg of grape seed powder and add 120 L of 70% ethanol aqueous solution (solid-liquid ratio 1:12). Use ultrasound-assisted extraction at 450 W, 35 °C, and 40 min. After filtration, combine the filtrates and recover the ethanol under reduced pressure to obtain polyphenol extract. This intermediate product plays a role in the preliminary enrichment of polyphenols in winemaking by-products, providing a substrate basis for subsequent enzymatic hydrolysis.

[0032] The pH of the polyphenol extract was adjusted to 4.8, and β-glucosidase was added at a concentration of 800 U / g of the total solids in the extract. The enzyme was hydrolyzed at 48°C for 2 hours to cleave glycosidic bonds and expose free phenolic hydroxyl groups. After hydrolysis, the enzyme was inactivated at 90°C for 10 minutes, and the solution was concentrated under reduced pressure to a total polyphenol concentration of 85 g / L to obtain an active polyphenol solution. This solution, through enzymatic hydrolysis to expose free phenolic hydroxyl groups, enhances the antioxidant and antibacterial activities of polyphenols. It also inhibits the activity of enzymes related to the decomposition of yeast amino acids in the early and middle stages of fermentation, thereby controlling the formation of higher alcohols.

[0033] Step 2: Esterification Grafting: Take 5 kg of microporous starch and add 11.5 L of purified water. Stir and disperse for 30 min to form a starch slurry with a mass concentration of approximately 30%. Under constant temperature and stirring speed at 40℃, first add a 10% sodium hydroxide solution dropwise to adjust the pH of the starch slurry to 8.5. Then, slowly add 2.0 kg of a mixture of hexanoic anhydride and butyric anhydride, where the mass ratio of hexanoic anhydride to butyric anhydride is 2:1, controlling the addition time to 40 min. During this addition process, continuously add the sodium hydroxide solution using a linked pH meter to dynamically maintain the pH of the reaction system at 8.0. Between 8.5;

[0034] After the addition was completed, the reaction continued for 2 hours. The reaction solution was adjusted to pH 7.0 with 1.0 mol / L hydrochloric acid solution, filtered, and the filter cake was washed with deionized water until the conductivity of the washing solution reached the preset pure water conductivity value. It was then dehydrated twice with anhydrous ethanol and vacuum dried at 45℃ for 12 hours to obtain short-chain fatty acid grafted microporous starch. The preparation process of this intermediate product did not introduce toxic solvents and met the fermentation safety requirements.

[0035] Step 3: Vacuum Impregnation and Assembly: The active polyphenol solution and short-chain fatty acid-grafted microporous starch were mixed at a mass ratio of 1.2:1, with ethanol as the solvent volume fraction at 50%, to obtain a mixed system. The mixed system was placed in a vacuum vessel, and a vacuum was drawn to an absolute pressure of 0.02 MPa and maintained for 30 min. After the vacuum was broken, the mixture was allowed to stand for another 40 min to allow the active polyphenols to be forced into the micropores. The solvent was removed by decompression evaporation at 35°C to obtain the loaded product. This product achieved the encapsulation of active polyphenols inside the microporous starch, preventing non-target volatilization or oxidation loss of polyphenols in the early stage of fermentation.

[0036] Step 4: Formation of functionalized fermentation control material: Prepare 10 L of 4% (w / w) water-soluble chitosan aqueous solution, uniformly disperse the loaded product in it, add genipin at a rate of 0.3% (w / w) of the water-soluble chitosan aqueous solution, and perform mild cross-linking pre-curing at 30℃ for 1.5 h; then perform spray drying at an inlet air temperature of 140℃ and an outlet air temperature of 75℃ to obtain a core-shell structure functionalized fermentation control material; the resulting material has a moisture content of 4.2% and an average particle size of 68 μm;

[0037] S3. Mixing and Fermentation in the Pit: Mix the cooked grains obtained in step S1 with 20kg of medium-temperature Daqu (fermentation starter), then add 0.26kg of the above-mentioned functional fermentation control material at 0.10% of the total mass of the mash. Mix well and then place in a mud pit for fermentation; after the first day in the pit... The temperature inside the cellar was controlled at 26℃ for 7 days, and on the 8th day... Controlled at 31℃ for 25 days, on the 26th The temperature naturally dropped to 28℃ over 60 days.

[0038] In the early stage of fermentation, the outer shell of the functional fermentation control material swells and exudes polyphenolic substances. In the middle and late stages of fermentation, as the pH value of the mash decreases and the ethanol concentration increases, the outer shell of the control material undergoes deep swelling, which increases the permeability of the cross-linked network. The functional fermentation control material has a core skeleton composed of short-chain fatty acids grafted with microporous starch. Under acidic conditions and the combined action of endogenous esterification enzymes in the mash system, the core skeleton breaks down and releases short-chain fatty acids, which combine with ethanol in the system and are converted in situ into corresponding ethyl ester flavor substances.

[0039] S4. Fermentation and distillation: Seal fermentation for 60 days, after which the liquor is removed from the cellar and distilled in a still. The liquor is then distilled in stages using conventional methods to obtain a base liquor with low content of higher alcohols.

[0040] The key indicator testing methods involved in this invention are as follows:

[0041] (1) Determination of the content of higher alcohols and esters: Gas chromatography was used; a sample of raw liquor was taken, and the internal standard n-amyl acetate was added and injected directly; a gas chromatograph was used; the injection port temperature was 250℃ and the detector temperature was 250℃; the temperature program was as follows: the initial temperature was 40℃, held for 3 min, increased to 150℃ at 4℃ / min, and then increased to 200℃ at 10℃ / min, held for 5 min; the carrier gas was high-purity nitrogen, the flow rate was 1.0 mL / min, and the split ratio was 20:1; qualitative analysis was based on the retention time, and quantitative analysis was based on the internal standard method.

[0042] (2) Determination of free polyphenol release rate: Take 10g of fermented mash at different stages of fermentation, add 50mL of 60% ethanol aqueous solution, extract at room temperature in the dark for 2h, centrifuge and take the supernatant; use the Folin-phenol colorimetric method to measure the absorbance at 765nm, use gallic acid as standard to prepare a standard curve, and calculate the free polyphenol content; Free polyphenol release rate = (measured free polyphenol content / theoretical loading of total polyphenols in functionalized fermentation control material) × 100%;

[0043] (3) Determination of total release of hexanoic acid and butyric acid: High performance liquid chromatography was used; 10g of fermented mash sample was taken, 50mL of deionized water was added, ultrasonic extraction was performed for 30min, centrifuged at 8000r / min for 10min, and the supernatant was filtered through a 0.22μm microporous membrane; High performance liquid chromatography was used, the chromatographic column was AminexHPX-87H (300mm×7.8mm), the mobile phase was 0.005mol / L sulfuric acid solution, the flow rate was 0.6mL / min, the column temperature was 50℃, the detection wavelength was 210nm, and the external standard method was used for quantification.

[0044] Example 2:

[0045] The only difference between this embodiment and Embodiment 1 is that the following parameters adopt the level of the lower limit or relative lower limit of the protection range parameters, while other operating steps and process parameters remain the same;

[0046] In step 1, the brewing byproduct was replaced with sorghum husks, the ethanol volume fraction was 50%, the material-to-liquid ratio was 1:10, the ultrasonic power was 400W, and the time was 30min; the β-glucosidase addition was 600U / g total solids, and the enzymatic hydrolysis temperature was 45℃. In step 2, the hexanoic anhydride to butyric anhydride mass ratio was 1:1, the esterification temperature was 30℃, the starch milk mass concentration was 30%, the reaction pH was maintained at 8.0, and the reaction time was 1h. In step 3, the active polyphenol solution used was a 40% ethanol aqueous solution. In step 4, the water-soluble chitosan aqueous solution mass concentration was 3%, the genipin addition was 0.1%, and the pre-curing time was 1h. The amount of functional fermentation control material added when entering the fermentation pit was 0.05% of the total mass of the mash.

[0047] Example 3:

[0048] The difference between this embodiment and Embodiment 1 is that the upper limit or relative upper limit parameter of the protection range is used, while other operating steps and process parameters remain the same;

[0049] In step 1, grape seed extraction uses an 80% (v / v) ethanol aqueous solution with a material-to-liquid ratio of 1:14, ultrasonic power of 500W, and time of 50 min; β-glucosidase is added at 1000 U / g total solids, and the enzymatic hydrolysis temperature is 50℃. In step 2, the mass ratio of hexanoic anhydride to butyric anhydride is 3:1, the esterification temperature is 50℃, the starch milk concentration is 40%, the reaction pH is maintained at 9.0, and the reaction time is 3 h. In step 3, the active polyphenol solution uses a 60% ethanol aqueous solution. In step 4, the water-soluble chitosan aqueous solution has a mass concentration of 5%, genipin is added at 0.5%, and pre-curing is performed for 2 h. The amount of functional fermentation control material added when entering the fermentation pit is 0.15% of the total mass of the mash.

[0050] Example 4:

[0051] The difference between this embodiment and Embodiment 1 is that a different set of intermediate parameters is used, while other operating steps and process parameters remain the same.

[0052] In step 1, the winemaking byproduct is grape seeds, the ethanol volume fraction is 60%, the material-to-liquid ratio is 1:11, the ultrasonic power is 420W, and the time is 35min; the β-glucosidase addition is 700U / g total solids, and the enzymatic hydrolysis temperature is 47℃. In step 2, the hexanoic anhydride to butyric anhydride mass ratio is 1.5:1, the esterification temperature is 35℃, the starch milk mass concentration is 35%, the reaction pH is maintained at 8.5, and the reaction time is 2.5h. In step 3, the active polyphenol solution uses a 45% ethanol aqueous solution. In step 4, the water-soluble chitosan aqueous solution mass concentration is 4.5%, the genipin addition is 0.4%, and the pre-curing time is 1.5h. The amount of functional fermentation control material added when entering the fermentation pit is 0.10% of the total mass of the mash.

[0053] Comparative Example 1:

[0054] The difference between this comparative example and Example 1 is that the β-glucosidase enzymatic hydrolysis in step 1 is omitted, and the polyphenol extract is directly concentrated and used for subsequent loading; other operating steps and process parameters are exactly the same as in Example 1.

[0055] Comparative Example 2:

[0056] The difference between this comparative example and Example 1 is that: in step 2, the esterification grafting of hexanoic anhydride and butyric anhydride is not performed, and ungrafted microporous starch is directly used for subsequent vacuum impregnation and microencapsulation; other operation steps and process parameters are exactly the same as in Example 1.

[0057] Comparative Example 3:

[0058] The difference between this comparative example and Example 1 is that the water-soluble chitosan-genipin responsive microencapsulation treatment in step 4 is omitted, and the loaded product obtained in step 3 is directly used as a fermentation control material after low-temperature drying; other operating steps and process parameters are exactly the same as in Example 1.

[0059] Comparative Example 4:

[0060] The difference between this comparative example and Example 1 is that the amount of functional fermentation control material added in step S3 is changed from 0.10% of the total mass of the mash to 0.02%; other operating steps and process parameters are exactly the same as in Example 1.

[0061] Comparative Example 5:

[0062] The difference between this comparative example and Example 1 is that the mass ratio of hexanoic anhydride to butyric anhydride in step 2 is changed from 2:1 to 5:1; other operating steps and process parameters are exactly the same as in Example 1.

[0063] To verify the technical effects of the solid-state fermentation method for reducing higher alcohol content in baijiu and the functionalized fermentation control materials provided by this invention, the aforementioned key index testing methods were used to systematically detect and collect data on the key nodes of the fermentation process in Examples 1-4 and Comparative Examples 1-5, as well as the final baijiu samples. The comparison results of the final physicochemical indicators of each group of samples are detailed in Table 1, and the monitoring data of the key nodes in the fermentation process are detailed in Table 2.

[0064] Table 1 Physicochemical properties of different samples

[0065] Sample number Isobutanol (mg / L) Isoamyl alcohol (mg / L) n-Propanol (mg / L) Total amount of higher alcohols (mg / L) Ethyl hexanoate (g / L) Ethyl butyrate (mg / L) Alcohol yield (L / 100kg sorghum) Example 1 215 455 190 860 2.06 186 34.8 Example 2 248 518 204 970 1.92 165 34.5 Example 3 232 486 198 916 1.98 178 34.4 Example 4 240 500 205 945 1.95 172 34.6 Comparative Example 1 305 635 240 1180 1.84 141 34.3 Comparative Example 2 338 690 262 1290 1.72 108 34.2 Comparative Example 3 322 650 238 1210 1.75 120 34.0 Comparative Example 4 352 720 278 1350 1.80 129 34.4 Comparative Example 5 286 590 224 1100 1.88 149 34.3

[0066] Table 2 Monitoring data of key nodes in the fermentation process

[0067] Group pH of mash on day 5 pH of mash on day 12 Ethanol volume fraction on day 12 Free polyphenol release rate on day 12 Total release of hexanoic acid and butyric acid on day 20 The increase in total esters on day 20 compared to the control group Example 1 5.42 4.05 5.8% 61% 428mg / kg of fermented mash 18.6% Example 2 5.48 4.11 5.6% 49% 336mg / kg of fermented mash 11.8% Example 3 5.39 4.02 5.9% 58% 402mg / kg of fermented mash 16.9% Example 4 5.44 4.08 5.7% 55% 381mg / kg of fermented mash 14.7% Comparative Example 1 5.43 4.06 5.8% 38% 421mg / kg of fermented mash 8.5% Comparative Example 2 5.41 4.04 5.8% 60% 86mg / kg of fermented mash 4.2% Comparative Example 3 5.40 4.05 5.7% 87% 435mg / kg of fermented mash 6.1% Comparative Example 4 5.44 4.07 5.7% 22% 96mg / kg of fermented mash 5.0% Comparative Example 5 5.42 4.05 5.8% 60% 301mg / kg of fermented mash 10.4%

[0068] As can be seen from the comparison of the test results of Example 1 and Comparative Example 1 in the table, after omitting the β-glucosidase enzymatic hydrolysis, the total amount of higher alcohols increased from 860 mg / L to 1180 mg / L, and the ethyl hexanoate decreased from 2.06 g / L to 1.84 g / L.

[0069] The underlying mechanism is that undigested polyphenols still contain a high proportion of glycoside-bound structures, resulting in insufficient exposure of free phenolic hydroxyl groups. This leads to stronger binding with proteins and cell walls in the fermentation system, and a decrease in the proportion of polyphenols diffusing into the liquid phase. On day 12, the release rate of free polyphenols decreased from 61% to 38%, indicating insufficient effective polyphenol concentration. This weakens the inhibitory effect on enzymes related to the degradation of yeast amino acids, while the conversion of leucine and valine to isoamyl alcohol and isobutanol remains at the upper limit. Therefore, higher alcohols are significantly increased. Insufficient polyphenol activity also weakens the regulation of contaminating bacteria and excessive oxidation reactions, reducing the utilization efficiency of acid precursors available for esterification in the mash, thus lowering ester levels.

[0070] Comparing the test results of Example 1 and Comparative Example 2 in the table, it can be seen that when short-chain fatty acid grafting was not performed, the total amount of higher alcohols increased to 1290 mg / L, ethyl hexanoate decreased to 1.72 g / L, and ethyl butyrate decreased to 108 mg / L.

[0071] The underlying mechanism is that ungrafted microporous starch only retains adsorption and loading functions and cannot provide a source of hexanoic acid and butyric acid release under slightly acidic conditions in the middle and late stages. Table 2 shows that the total release of hexanoic acid and butyric acid on day 20 was only 86 mg / kg mash, lower than 428 mg / kg mash in Example 1. The acid substrate used for in-situ esterification with ethanol in the system did not reach the threshold required for the reaction, and the production of ethyl hexanoate and ethyl butyrate decreased accordingly. Insufficient acid substrate also weakens the traction effect on yeast metabolic diversion, and more carbon flow is diverted to the higher alcohol synthesis branch, thus increasing the total amount of higher alcohols.

[0072] As can be seen from the comparison of the test results of Example 1 and Comparative Example 3 in the table, after omitting the responsive microencapsulation, the total amount of higher alcohols increased from 860 mg / L to 1210 mg / L, and the ethyl hexanoate decreased from 2.06 g / L to 1.75 g / L.

[0073] The underlying mechanism is that, without the outer shell formed by water-soluble chitosan-genipin, polyphenols and grafted acid groups diffuse more rapidly in the early stages of fermentation. By day 12, the release rate of free polyphenols reached 87%, significantly higher than in Example 1. This premature release leads to the loss of active substances due to non-target adsorption, oxidation, or volatilization in the early stages of fermentation. When it is truly necessary to inhibit the formation of higher alcohols in the later stages, the effective concentration in the system actually decreases. At the same time, the earlier release of acid groups is not conducive to matching with the ethanol accumulated in the later stages, resulting in a decrease in esterification efficiency. Therefore, the higher alcohols exceed the set threshold, and the amount of esters generated is lower than expected.

[0074] As can be seen from the comparison of the test results of Example 1 and Comparative Example 4 in the table, after reducing the amount of functionalized fermentation control material from 0.10% to 0.02%, the total amount of higher alcohols increased to 1350 mg / L, and ethyl hexanoate decreased to 1.80 g / L;

[0075] The underlying mechanism is that insufficient material addition reduces the regulatory intensity at two levels: first, the effective release of polyphenols decreases, with the free polyphenol release rate at day 12 being only 22%, which is insufficient to stably inhibit the higher alcohol synthesis pathway in yeast; second, the total amount of releaseable hexanoic acid and butyric acid does not reach the threshold required for the reaction, with only 96 mg / kg of mash detected at day 20, making it impossible to continuously replenish the esterification substrate; therefore, higher alcohols do not show a substantial decrease, and the increase in esters is also relatively small.

[0076] As can be seen from the comparison of the test results of Example 1 and Comparative Example 5 in the table, after changing the mass ratio of hexanoic anhydride to butyric anhydride from 2:1 to 5:1, the total amount of higher alcohols increased to 1100 mg / L, while ethyl hexanoate and ethyl butyrate decreased to 1.88 g / L and 149 mg / L, respectively.

[0077] The underlying mechanism is that an imbalance in the composition of grafted acid groups alters the hydrolysis behavior and esterification substrate ratio of the material in the mid-to-late stages. When the proportion of hexanoyl groups is too high, the hydrophobicity of the material surface increases, and the local hydrolysis rate decreases. In Table 2, the total release of hexanoic acid and butyric acid is 301 mg / kg of mash, which is lower than in Example 1. At the same time, insufficient butyryl groups limit the formation of ethyl butyrate, resulting in a decrease in ester aroma. When the acid group release efficiency and ratio are not suitable, the pulling effect on carbon flow and amino acid metabolism in the fermentation system is weakened, so the control effect of higher alcohols is not as good as in Example 1.

[0078] The comparison of the test results of Examples 1 and Examples 2 to 4 in the table shows that all four examples can reduce higher alcohols and increase esters while maintaining a basically stable alcohol yield. However, the data of Example 1 is more balanced. Example 2 uses the lower limit parameters for extraction intensity, esterification degree, and addition amount, resulting in lower polyphenol release rate and acid release. Therefore, the control of higher alcohols and the increase of esters are limited.

[0079] Example 3, using the upper limit parameters for extraction intensity, esterification degree, and addition amount, can provide more active components, but when the degree of shell cross-linking reaches the upper limit, the release rate is relatively delayed, and the addition amount of the upper limit parameter has a certain inhibitory effect on yeast growth. Therefore, the data does not exceed that of Example 1. In Example 4, all parameters are at the intermediate level, and the fermentation performance is stable, but the inhibition of higher alcohols and the increase of esters are both lower than those of Example 1.

[0080] As can be seen from Tables 1 and 2, the enzymatic release of active polyphenols, the construction of short-chain fatty acid-grafted microporous starch, the responsive shell formed by water-soluble chitosan-genipin, and the appropriate dosage jointly determine the temporal release behavior of this material in solid-state fermentation. When this temporal behavior is matched with the acidity of the mash and the ethanol accumulation process, the formation of isobutanol, isoamyl alcohol, and n-propanol can be reduced without significantly affecting the alcohol yield, while increasing the content of ethyl hexanoate and ethyl butyrate.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any conventional modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for brewing baijiu (Chinese white liquor) using solid-state fermentation to reduce the content of higher alcohols, comprising the following steps: S1, Raw material processing: The brewing grain raw materials are crushed, moistened, steamed, and then cooled and maintained at 20°C. At 25℃, the cooled brewing grain raw materials were obtained; S2, Combination of fermentation agent and regulating material: Daqu (a type of starter culture) is added to the cooled brewing grain raw material and mixed, while functional fermentation regulating material is added simultaneously to obtain fermented mash. The amount of functional fermentation regulating material added is 0.05% of the total mass of the fermented mash. 0.15%; The functionalized fermentation control material is a microcapsule with a core-shell structure, the outer shell of which is composed of cross-linked water-soluble chitosan, and the core skeleton is short-chain fatty acid grafted microporous starch loaded with active polyphenol solution in the internal micropores. S3, Solid-state fermentation: The mash is placed in a fermentation pit for solid-state fermentation; in the early stage of fermentation, the outer shell of the functional fermentation control material swells and exudes polyphenolic substances; in the middle and late stages of fermentation, as the pH value of the mash decreases and the ethanol concentration increases, the outer shell undergoes deep swelling, which increases the permeability of the cross-linked network. Under the combined action of acidic conditions and endogenous esterification enzymes in the mash system, the core skeleton breaks down and releases short-chain fatty acids, which combine with ethanol in the system and are converted in situ into corresponding ethyl ester flavor substances; S4, Distillation: After fermentation, the fermented mash is removed from the cellar and distilled in a still, and the liquor is separated in stages to obtain a base liquor with low content of higher alcohols.

2. The method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 1, wherein the preparation method of the functionalized fermentation control material includes the following steps: Step (1) Extraction and enzymatic hydrolysis: Ultrasonic-assisted extraction with a volume fraction of 50% was used. Polyphenols were extracted from brewing byproducts using an 80% ethanol aqueous solution, and the ethanol was recovered under reduced pressure to obtain a polyphenol extract. β-glucosidase was added to the polyphenol extract for isothermal enzymatic hydrolysis to cleave the glycosidic bonds and expose the free phenolic hydroxyl groups. The enzyme was then inactivated and the extract was concentrated to obtain an active polyphenol solution. Step (2) Esterification Grafting: Microporous starch is dispersed in purified water to form a starch emulsion. Food-grade alkali solution is added dropwise to adjust and maintain the pH of the system at a weakly alkaline level. The mass of the microporous starch is 30% of the total mass of the microporous starch added under constant stirring. A mixture of 50% hexanoic anhydride and butyric anhydride, wherein the mass ratio of hexanoic anhydride to butyric anhydride is 1:

1. 3:1, at a temperature of 30 Esterification reaction was carried out at 50℃ 1 3h; after the reaction is complete, neutralize to neutral with food-grade acid, and then wash with water, dehydrate with anhydrous ethanol and vacuum dry to obtain short-chain fatty acid grafted microporous starch with hexanoyl and butyryl groups. Step (3) Vacuum impregnation and assembly: Dissolve the active polyphenol solution in a solution with a volume fraction of 40%. In a 60% ethanol aqueous solution, the short-chain fatty acid-grafted microporous starch was added and mixed to obtain a mixed system. The mixed system was placed in a vacuum vessel, evacuated, and maintained for 30 minutes. Then, the vacuum was broken to force the active polyphenol solution into the micropores of the short-chain fatty acid-grafted microporous starch. The solvent was removed by evaporation under reduced pressure at 40°C to obtain the supported product. Step (4) Formation of functionalized fermentation control material: The loaded product is uniformly dispersed in a water-soluble chitosan aqueous solution, and 0.1% of the mass of the water-soluble chitosan aqueous solution is added. 0.5% crosslinking agent genipin, at a temperature of 25°C Mild cross-linking pre-curing was performed at 40℃ 1 After 2 hours, the functionalized fermentation control material with a core-shell structure was obtained by spray drying.

3. The solid-state fermentation method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 1, characterized in that, In step S3, the temperature control process for solid-state fermentation is as follows: after entering the fermentation pit, the first... The temperature inside the cellar was controlled at 26℃ for 7 days, and on the 8th day... The temperature was controlled at 31℃ on day 25, and on the 26th... The temperature naturally dropped to 28℃ after 60 days.

4. The solid-state fermentation method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 1, characterized in that, In step S3, after the fermented mash is placed in the cellar 1 After 5 days, the outer shell of the functionalized fermentation control material swells and exudes polyphenolic substances.

5. A method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 2, characterized in that, In step (2), the mass concentration of the starch milk is 30%. 40%, the food-grade alkali solution has a mass fraction of 5%. A 10% sodium hydroxide solution, the weakly alkaline pH being 8.

0. 9.

0.

6. The solid-state fermentation method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 2, characterized in that, In step (3), the vacuuming process conditions are: vacuuming to an absolute pressure of 0.02 MPa and maintaining it for 30 minutes.

7. The solid-state fermentation method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 2, characterized in that, In step (4), the mass concentration of the water-soluble chitosan aqueous solution is 3%. 5%.

8. A method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 2, characterized in that, In step (4), the spray drying process conditions are: inlet air temperature of 140°C and outlet air temperature of 75°C.

9. A method for brewing baijiu (Chinese liquor) with reduced higher alcohol content according to claim 2, characterized in that, In step S3, the fermented mash is placed into the cellar 10. After 15 days, the pH of the mash decreased to 3.

2. Within the 4.0 range and with the accumulation of ethanol concentration, the outer shell of the functionalized fermentation control material undergoes deep swelling, increasing the permeability of the cross-linked network. Under acidic conditions and with the combined action of endogenous esterifying enzymes in the mash system, the hexanoyl and butyryl groups grafted into the core skeleton break down and release hexanoic acid and butyryl acid, which then combine with ethanol in the system to convert into ethyl hexanoate and ethyl butyrylate.