A method for brewing a sorghum beer

Abstract

The application discloses a kind of brewing methods of sorghum beer. Including the following steps: after being crushed, sorghum is mixed with barley malt, and gelatinization treatment is carried out;Using subsection heating process for saccharification;The wort after saccharification is filtered and washed;The wort obtained by filtering is boiled, and composite hops are added in stages during boiling;After boiling, whirl sedimentation, cooling, yeast is added to fermentation, and sorghum beer is obtained.The advantages of the present application are: 1) the composite hops composed of gusbruk and honey melon dragon, the two form complementary advantages in aroma components, synergistically improve the richness and persistence of beer aroma, the total ester content is increased to more than 4.8 mg / L, and the aroma retention time is extended to more than 21 days;2) by optimizing the saccharification process parameters, efficient conversion of sorghum starch is realized, and the wort concentration reaches 14 °P;3) stable and controllable process, suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of beer brewing technology, specifically to a method for brewing beer using sorghum as a raw material, and more particularly to a method for brewing sorghum beer using compound hops to synergistically enhance aroma. Background Technology

[0002] Sorghum is the world's fifth largest grain crop, possessing excellent characteristics such as drought resistance, flood resistance, and salt tolerance, and is widely cultivated in arid and semi-arid regions globally. Sorghum grains contain over 70% starch and have moderate protein content, making them an excellent brewing raw material. Compared to other brewing grains, sorghum is relatively inexpensive and gluten-free, making it an ideal choice for developing gluten-free beer. However, sorghum starch has a relatively high gelatinization temperature (65–80°C), making it difficult to fully gelatinize in traditional beer mashing processes, resulting in incomplete starch breakdown and low mashing efficiency.

[0003] There are already reports of using sorghum in beer brewing. For example, some patent documents describe using sorghum flour to replace rice and part of the malt, brewing pale sorghum beer through gelatinization, saccharification, and fermentation. However, this technology involves a gelatinization time of only 10-20 minutes and a single-stage saccharification temperature of 70°C, resulting in limited saccharification efficiency and low wort concentration. Furthermore, the original wort concentration of existing sorghum beer products is typically 11-12°P, which is insufficient to meet the quality requirements of high-concentration craft beer.

[0004] In hop application, the types and contents of volatile organic compounds (VOCs) vary significantly among different hop varieties, directly affecting the aroma characteristics and quality of beer. Terpenes, esters produced by yeast fermentation, and higher alcohols in hops are important sources of beer aroma. Studies have shown that when hops with different aroma types are mixed, their aroma components are not simply additive, but may produce a synergistic effect, resulting in a more prominent hop aroma in the beer. Hersbrucker is a traditional German aroma hop with an α-acid content of 1.5–5.0% and a geraniol content of 15–30%. It has floral, herbal, hay, and citrus aromas, a clean and mellow bitterness, and an excellent balance between aroma and bitterness. Nectaron (HORT4337) is a modern flavor hop developed in New Zealand. It contains 9.5–12% alpha-acid and a high geraniol content of 59–65%, exhibiting strong tropical fruit aromas such as pineapple, passion fruit, peach, and citrus. However, there are currently no reports on the use of this combination of hops in brewing sorghum beer.

[0005] Therefore, developing a brewing method for sorghum beer that can achieve high concentration and excellent aroma quality has significant application value and market prospects. Summary of the Invention

[0006] To address the problems of low saccharification efficiency, difficulty in increasing wort concentration, and poor aroma quality in existing sorghum beer brewing methods, this invention provides a sorghum beer brewing method.

[0007] In response to the above-mentioned technical problems, this invention proposes the following technical solutions through in-depth research and process optimization.

[0008] A method for brewing sorghum beer, characterized by comprising the following steps: (1) Raw material pretreatment: After crushing the sorghum, mix it with barley malt in a certain proportion, add water for gelatinization treatment, the gelatinization temperature is 95-105℃, and the gelatinization time is 50-70min; (2) Saccharification: The gelatinized mash is saccharified by heating in stages, successively heating to 53-55℃ and holding for 25-35 min, 62-64℃ and holding for 25-35 min, 68-70℃ and holding for 35-45 min, and 77-79℃ and holding for 12-18 min; (3) Filtration: The saccharified wort is pumped into a filter tank for filtration, the first wort is collected, and then the slag is washed and the washed wort is collected. (4) Boiling: Boil the filtered wort at a temperature of 97-98°C for 60-80 minutes. During the boiling process, add compound hops in stages. The compound hops are composed of Hersbrucker and Nectaron in a mass ratio of 40:60-70:30. (5) Whirlpool sedimentation: The boiled wort is poured into a whirlpool sedimentation tank, allowed to settle and swirl, and then pre-cooled to 16-20°C; (6) Fermentation: Inoculate the cooled wort with yeast for fermentation at a temperature of 11-15°C until the sugar content drops to the target value to obtain sorghum beer.

[0009] In step (1), the control of the sorghum particle size has a significant impact on the gelatinization effect. If the sorghum is ground too coarsely, the starch particles will not be fully exposed, affecting the gelatinization efficiency; if it is ground too finely, it will lead to filtration difficulties. This invention uses a conventional particle size (approximately 40-60 mesh). Boiling at 95-105℃ for 50-70 minutes allows the sorghum starch to be fully gelatinized, causing the starch particles to absorb water, swell, and rupture, releasing soluble starch and providing sufficient substrate for subsequent saccharification. If the gelatinization temperature is too low or the time is too short, the sorghum starch will not be fully gelatinized, leading to a decrease in saccharification efficiency; if the gelatinization temperature is too high or the time is too long, it may cause energy waste and increase the formation of Maillard reaction products, affecting the color and flavor of the beer.

[0010] In step (2), segmented heating saccharification is one of the key technologies of this invention. Maintaining a temperature of 53–55℃ is beneficial for the activity of β-glucanase and protease, decomposing β-glucan and protein in the wort, reducing wort viscosity, and improving filtration performance. 62–64℃ is the optimal operating temperature for β-amylase, at which temperature β-amylase decomposes fermentable sugar chains into maltose, increasing the fermentable sugar content of the wort. 68–70℃ is the optimal operating temperature for α-amylase, which decomposes gelatinized starch into dextrin and oligosaccharides. Maintaining a temperature of 77–79℃ can terminate the enzyme reaction and reduce wort viscosity. The combined design of the four temperature platforms ensures both sufficient saccharification of sorghum starch and efficient generation of fermentable sugars.

[0011] In step (3), the filtration process combines first-run wort separation with multiple washing of the spent grains. First-run wort separation collects the high-concentration first wort, while multiple washing of the spent grains can fully remove the soluble extracts remaining in the spent grains, thereby improving the utilization rate of raw materials.

[0012] In step (4), the use of compound hops is another key technical feature of this invention. Hersbrucker is a traditional German aroma hop with an α-acid content of 1.5–5.0%, a total oil content of 0.5–1.0 mL / 100g, and a geraniol content of 15–30%, mainly exhibiting floral, herbal, hay, and citrus aromas. Nectaron is a modern flavor hop developed in New Zealand with an α-acid content of 9.5–12%, a total oil content of 1.5–2.0 mL / 100g, and a geraniol content of 55–65%, mainly exhibiting strong tropical fruit aromas such as pineapple, passion fruit, peach, and grapefruit. The inventors unexpectedly discovered that when Hersbrucker and Nectaron are used in combination at a mass ratio of 40:60–70:30, the aroma components of the two hops can produce a synergistic effect, making the aroma richness and persistence of the beer significantly better than when either is used alone.

[0013] In step (5), vortex precipitation can effectively separate hot solids, and pre-cooling to 16-20℃ can cause the cold solids to precipitate in advance, reducing the generation of undesirable flavor substances during fermentation and improving the flavor stability of beer.

[0014] In step (6), the fermentation temperature is controlled at 11-15℃, which is within the typical low-temperature fermentation range for lager beer. Low-temperature fermentation helps retain the volatile aroma compounds in the wort while reducing the formation of undesirable flavor compounds such as higher alcohols, resulting in a purer beer taste.

[0015] As a further improvement of the present invention, the mass ratio of sorghum to barley malt in step (1) is 20:80 to 40:60. When the amount of sorghum used is too low, the cost advantage is not obvious and the characteristic flavor of sorghum is not prominent; when the amount of sorghum used is too high, due to the low enzyme activity in sorghum, it may lead to a decrease in saccharification efficiency and difficulty in filtration. Through a large number of experiments, the inventors have found that when the mass ratio of sorghum to barley malt is in the range of 20:80 to 40:60, both saccharification efficiency and wort quality are guaranteed, while giving full play to the economic advantages and flavor characteristics of sorghum as a brewing raw material.

[0016] As a further improvement of the present invention, the total amount of compound hops added in step (4) is 150-300g per ton of wort. Through experiments, the inventors have found that when the total amount of compound hops added is within this range, the bitterness and aroma intensity of the beer are in optimal balance. If the amount added is too small, the bitterness is insufficient and the aroma is weak; if the amount added is too large, the bitterness is too strong, which may mask the original flavors of the malt and sorghum.

[0017] As a further improvement of the present invention, the specific operation of adding compound hops in step (4) is as follows: add Gusbrook 4-6 minutes after the start of boiling, and add Melon hops 13-18 minutes before the end of boiling. Adding Gusbrook at the beginning of boiling allows its α-acids to be fully isomerized, contributing a clean and mellow bitterness skeleton; adding Melon hops at the end of boiling can maximize the retention of its rich volatile aroma components, giving the beer a strong tropical fruit aroma.

[0018] As a further improvement of the present invention, the heating rate of the segmented heating saccharification in step (2) is 1-2 °C / min. Controlling the heating rate within a slower range allows the enzyme reaction in each temperature segment to proceed fully, while avoiding the adverse effects of sudden temperature changes on enzyme activity.

[0019] As a further improvement of the present invention, the washing of the lees in step (3) is carried out in three stages, with the washing water temperature being 76-80°C and the total washing water volume being 0.8-1.2 times the volume of wort. Washing the lees in stages helps to fully remove the soluble extractives remaining in the lees, improving the utilization rate of the raw materials. The washing water temperature of 76-80°C can reduce the viscosity of the wort and improve filtration efficiency. If the water temperature is too low, residual sugar will not be washed away completely; if the water temperature is too high, a large amount of viscous substances will be washed out and α-amylase will be destroyed.

[0020] As a further improvement of the present invention, the vortex sedimentation time in step (5) is 20-40 min, and the precooling flow rate is 80-120 L / min. The vortex sedimentation time of 20-40 min can ensure that the hot coagulated material settles sufficiently; the precooling flow rate of 80-120 L / min can cool the wort to the target temperature in a shorter time and reduce aroma loss.

[0021] As a further improvement of the present invention, the yeast mentioned in step (6) is Saccharomyces pastorianus, and the inoculation amount is 0.5 to 1.0 kg per ton of wort. Saccharomyces pastorianus has good low-temperature fermentation performance and moderate ester production, making it suitable for brewing sorghum beer with pure aroma and refreshing taste.

[0022] As a further improvement of the present invention, the fermentation in step (6) includes primary fermentation and secondary fermentation. The primary fermentation temperature is 11-14°C, and fermentation is carried out until the sugar content drops below 4.0°P, after which the beer is sealed and pressurized. The secondary fermentation temperature is 12-14°C, and fermentation is carried out under pressure until the sugar content drops below 3.5°P. During the primary fermentation stage, yeast multiplies rapidly and carries out alcoholic fermentation, resulting in a rapid decrease in sugar content. Sealing and pressurizing promote the generation of aroma substances such as esters. During the secondary fermentation stage, yeast further metabolizes undesirable flavor substances such as diacetyl, making the beer flavor more mature and stable.

[0023] This invention also discloses a sorghum beer produced by the above-described brewing method. This sorghum beer has advantages such as rich aroma, harmonious taste, and stable flavor.

[0024] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention achieves efficient saccharification of sorghum starch through a segmented heating saccharification process (four-stage heat preservation at 53-55℃ / 62-64℃ / 68-70℃ / 77-79℃) and optimized gelatinization conditions (95-105℃ / 50-70min), with a wort concentration of 14°P, which is significantly higher than that of existing sorghum beer products (usually 11-12°P).

[0025] 2) This invention uses a composite hop mixture of Goosebrook and Melon, where the aroma components of the two hops produce a synergistic effect. Experiments have shown that when the mass ratio of Goosebrook to Melon is 60:40, the total ester content of the beer reaches 4.85 mg / L, which is significantly higher than that of using Goosebrook alone (3.12 mg / L) and Melon alone (3.98 mg / L), and the aroma retention time (21 days) is significantly better than that of using either hop alone (14 days and 16 days, respectively).

[0026] 3) The brewing method of the present invention is stable and controllable, and is suitable for large-scale industrial production. Detailed Implementation

[0027] To enable those skilled in the art to better implement the present invention, the present invention will be further described below with reference to embodiments. However, it should be understood that the present invention is not limited to the following embodiments.

[0028] For ease of comparison, the raw materials used in the following examples and comparative examples are all from the same batch, and the specific parameters of the raw materials are as follows: Sorghum: Jinnuo No. 3 glutinous sorghum, starch content ≥70%, commercially available; Barley malt: High-quality imported barley malt, saccharification power ≥250WK, commercially available; Hersbrucker hops: α-acid content 1.5–5.0%, total oil content 0.5–1.0 mL / 100g, produced in Germany; Nectaron (HORT4337) hops: α-acid content 9.5-12%, total oil content 1.5-2.0 mL / 100g, from New Zealand; Lager yeast: Saccharomyces pastorianus, a commercial lager yeast strain; Gypsum (CaSO4·2H2O): Food grade, commercially available; Calcium chloride (CaCl2): Food grade, commercially available; Lactic acid: food grade, commercially available; Deionized water: prepared in the laboratory, meeting the standards for brewing water.

[0029] Example 1: Brew sorghum beer according to the following method (based on a trial production of 2.5 tons): S1. Raw material pretreatment: Weigh 150 kg of sorghum and grind it to 40-60 mesh; weigh 350 kg of barley malt and grind it for later use. Mix the ground sorghum and barley malt evenly, add about 1600 L of water, heat to 100℃, and boil to gelatinize for 60 min.

[0030] S2. Saccharification: The gelatinized mash is saccharified by staged heating at a rate of 1.5℃ / min. The specific operation is as follows: S2-1. Heat to 54℃, steam pressure 0.5MPa, cut off steam at 53℃ in advance, and keep warm for 30 minutes; S2-2, Heat to 63℃, steam pressure 0.8MPa, cut off steam at 62℃, and keep warm for 30 minutes; S2-3. Heat to 69℃, steam pressure 0.8MPa, cut off steam at 67℃, and keep warm for 40 minutes; S2-4. Heat to 78℃, steam pressure 0.8MPa, cut off steam at 77℃, and keep warm for 15 minutes.

[0031] The stirring speed during saccharification is adjusted according to the stage, ranging from 15 to 85 r / min.

[0032] S3. Filtration: The mashed wort is pumped into a filter tank for filtration. After preheating the filter tank, a bottom layer of water (80℃, 120L) is added, followed by static deep tillage and reflux. Approximately 1200L of first wort is collected. Then, the wort is washed in three stages: first wash with 600L of water at a flow rate of 50L / min; second wash with 600L of water at a flow rate of 80L / min; and third wash with 400L of water at a flow rate of 100L / min. The washing water temperature is 78℃. Approximately 1600L of washed wort is collected and combined with the first wort.

[0033] S4. Boiling: Pour the combined wort into the boiling kettle, control the boiling temperature at 97.5℃, and boil for a total of 70 minutes. The blended hops consist of Gusbrook and Melon hops in a mass ratio of 60:40, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add in stages: Add Gusbrook (300g) 5 minutes after the start of boiling, and add Melon hops (200g) 15 minutes before the end of boiling.

[0034] S5. Whirlpool sedimentation: The boiled wort is poured into a whirlpool sedimentation tank and allowed to settle for 30 minutes to separate the hot coagulated matter. Then, it is pre-cooled to 18°C ​​at a cooling flow rate of 100 L / min and circulated for 2.5 minutes.

[0035] S6. Fermentation: The cooled wort is inoculated with lager yeast at a rate of 0.6 kg per ton of wort (i.e., 1.5 kg for 2.5 tons of wort). The primary fermentation temperature is 12–14°C. Fermentation continues until the sugar content drops below 4.0°P, at which point the container is sealed and pressurized. The secondary fermentation temperature is 12–14°C, and fermentation continues under pressure until the sugar content drops below 3.5°P. Temperature, pressure, and sugar content changes are monitored regularly during fermentation. After fermentation, the temperature is lowered to 0°C, and the beer is stored and matured to obtain sorghum beer, designated as Sample 1.

[0036] Example 2: The procedure is the same as in Example 1, except that the gelatinization temperature, gelatinization time, and segmented saccharification holding temperature are adjusted. The specific scheme is as follows: S1. Raw material pretreatment: Weigh 150 kg of sorghum and grind it to 40-60 mesh; weigh 350 kg of barley malt and grind it for later use. Mix the ground sorghum and barley malt evenly, add about 1600 L of water, heat to 95℃, and boil to gelatinize for 70 min.

[0037] S2. Saccharification: The gelatinized mash is saccharified by staged heating at a rate of 1℃ / min. The specific operation is as follows: S2-1. Heat to 53℃, steam pressure 0.5MPa, cut off steam at 52℃ in advance, and keep warm for 35 minutes; S2-2, Heat to 62℃, steam pressure 0.8MPa, cut off steam at 61℃, and keep warm for 35 minutes; S2-3. Heat to 68℃, steam pressure 0.8MPa, cut off steam at 67℃, and hold for 45 minutes; S2-4. Heat to 77℃, steam pressure 0.8MPa, cut off steam at 76℃, and hold for 18 minutes.

[0038] The stirring speed during saccharification is adjusted according to the stage, ranging from 15 to 85 r / min.

[0039] S3, same as step S3 in Example 1.

[0040] S4, the compound hops consist of Gusbrook and Melon hops in a mass ratio of 40:60, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add in stages: add Gusbrook (200g) 4 minutes after boiling begins, and add Melon hops (300g) 18 minutes before boiling ends.

[0041] S5, vortex precipitation: static vortex precipitation for 20 min, pre-cool to 16℃, cooling flow rate 80 L / min, circulation for 2.5 min.

[0042] S6. Fermentation: The cooled wort was inoculated with lager yeast at a rate of 0.5 kg per ton of wort (i.e., 1.25 kg for 2.5 tons of wort). The primary fermentation temperature was 11–14°C. Fermentation continued until the sugar content dropped below 4.0°P, at which point the container was sealed and pressurized. The secondary fermentation temperature was 12–14°C, and fermentation continued under pressure until the sugar content dropped below 3.5°P. Temperature, pressure, and sugar content changes were monitored regularly during fermentation. After fermentation, the temperature was lowered to 0°C, and the beer was stored and matured to obtain sorghum beer, designated as Sample 2.

[0043] Example 3: The procedure is the same as in Example 1, except that the gelatinization temperature, gelatinization time, and segmented saccharification holding temperature are adjusted. The specific scheme is as follows: S1. Raw material pretreatment: Weigh 150 kg of sorghum and grind it to 40-60 mesh; weigh 350 kg of barley malt and grind it for later use. Mix the ground sorghum and barley malt evenly, add about 1600 L of water, heat to 105℃, and boil to gelatinize for 50 min.

[0044] S2. Saccharification: The gelatinized mash is saccharified by staged heating at a rate of 2℃ / min. The specific operation is as follows: S2-1. Heat to 55℃, steam pressure 0.5MPa, cut off steam at 54℃ in advance, and keep warm for 25 minutes; S2-2, Heat to 64℃, steam pressure 0.8MPa, cut off steam at 63℃, and keep warm for 25 minutes; S2-3. Heat to 70℃, steam pressure 0.8MPa, cut off steam at 69℃, and keep warm for 35 minutes; S2-4. Heat to 79℃, steam pressure 0.8MPa, cut off steam at 78℃, and keep warm for 12 minutes.

[0045] The stirring speed during saccharification is adjusted according to the stage, ranging from 15 to 85 r / min.

[0046] S3, same as step S3 in Example 1.

[0047] S4, the compound hops consist of Gusbrook and Melon hops in a mass ratio of 70:30, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add in stages: add Gusbrook (350g) 6 minutes after boiling begins, and add Melon hops (150g) 13 minutes before boiling ends.

[0048] S5, vortex precipitation: static vortex precipitation for 40 min, pre-cool to 20℃, cooling flow rate 120 L / min, circulation for 2.5 min.

[0049] S6. Fermentation: The cooled wort is inoculated with lager yeast at a rate of 1.0 kg per ton of wort (i.e., 2.5 kg for 2.5 tons of wort). The primary fermentation temperature is 12–14℃, and fermentation continues until the sugar content drops below 4.0°P, at which point the container is sealed and pressurized. The secondary fermentation temperature is 12–14℃, and fermentation continues under pressure until the sugar content drops below 3.5°P. Temperature, pressure, and sugar content changes are monitored regularly during fermentation. After fermentation, the temperature is lowered to 0℃, and the beer is stored and matured to obtain sorghum beer, designated as Sample 3.

[0050] Comparative Example 1: This comparative example is a control experiment of Example 1, conducted according to the same steps as Example 1, with the difference that: Melaleuca hops were not added; that is, only Gusbruck hops were used in the compound hops, and the total addition amount was 200g per ton of wort (i.e., 500g added for 2.5 tons of wort). The specific scheme is as follows: S1, same as step S1 in Example 1.

[0051] S2, same as step S2 in Example 1.

[0052] S3, same as step S3 in Example 1.

[0053] S4. Use only Gusbrook hops, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add all Gusbrook hops at once, 5 minutes after boiling begins.

[0054] S5, same as step S5 in Example 1.

[0055] S6, same as step S6 in Example 1.

[0056] The resulting sorghum beer was designated as control sample D1.

[0057] Comparative Example 2: This comparative example is a control experiment of Example 1, conducted according to the same steps as Example 1, with the difference that: Gusbruck hops were not added, that is, only Melaleuca hops were used in the compound hops, and the total addition amount was 200g per ton of wort (i.e., 500g was added for 2.5 tons of wort). The specific scheme is as follows: S1, same as step S1 in Example 1.

[0058] S2, same as step S2 in Example 1.

[0059] S3, same as step S3 in Example 1.

[0060] S4. Use only hops called "Micahlon" (or "Hops"), with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add all hops at once, 15 minutes before the end of boiling.

[0061] S5, same as step S5 in Example 1.

[0062] S6, same as step S6 in Example 1.

[0063] The resulting sorghum beer was designated as control sample D2.

[0064] Comparative Example 3: This comparative example is a control experiment of Example 1, conducted according to the same steps as Example 1, except that the mass ratio of Gusbruck to Melon in the compound hops was adjusted beyond the range defined in this invention (40:60-70:30), specifically to 80:20. The specific scheme is as follows: S1, same as step S1 in Example 1.

[0065] S2, same as step S2 in Example 1.

[0066] S3, same as step S3 in Example 1.

[0067] S4, the compound hops consist of Gusbrook and Melon hops in a mass ratio of 80:20, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add in stages: add Gusbrook (400g) 5 minutes after boiling begins, and add Melon hops (100g) 15 minutes before boiling ends.

[0068] S5, same as step S5 in Example 1.

[0069] S6, same as step S6 in Example 1.

[0070] The resulting sorghum beer was designated as control sample D3.

[0071] Comparative Example 4: This comparative example is a control experiment of Example 1, conducted according to the same steps as Example 1, except that the mass ratio of Goosebrook to Melon in the compound hops was adjusted beyond the range defined in this invention (40:60-70:30), specifically to a mass ratio of Goosebrook to Melon of 20:80. The specific scheme is as follows: S1, same as step S1 in Example 1.

[0072] S2, same as step S2 in Example 1.

[0073] S3, same as step S3 in Example 1.

[0074] S4, the compound hops consist of Gusbrook and Melon hops in a mass ratio of 20:80, with a total addition of 200g per ton of wort (i.e., 500g for 2.5 tons of wort). Add in stages: add Gusbrook (100g) 5 minutes after boiling begins, and add Melon hops (400g) 15 minutes before boiling ends.

[0075] S5, same as step S5 in Example 1.

[0076] S6, same as step S6 in Example 1.

[0077] The resulting sorghum beer was designated as control sample D4.

[0078] Performance verification experiment: The sorghum beer samples prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to physicochemical index determination and aroma quality evaluation.

[0079] Experimental methods: (1) Determination of total ester content: The ester content in beer samples was determined by gas chromatography, referring to the determination method of esters in GB / T 4928-2008 "Methods for Analysis of Beer".

[0080] About 60 different esters have been found in beer, among which the key esters that have the greatest impact on beer flavor include: ethyl acetate (solvent / fruit flavor), isoamyl acetate (banana / fruit flavor), isobutyl acetate (fruit flavor), β-phenyl acetate (floral / rose / honey flavor), ethyl hexanoate (apple / pear / pineapple), and ethyl octanoate (apricot / pineapple).

[0081] Instrument conditions: A DM-WAX capillary column (30m × 0.53mm × 2μm) and a flame ionization detector (FID) were used; the injection port temperature was 200℃, and the detector temperature was 230℃; the column temperature was programmed: 40℃ for 3 min, increased to 90℃ at 10℃ / min and held for 1 min, then increased to 220℃ at 30℃ / min and held for 3 min. Sample pretreatment: 5 mL of undegassed beer was placed in a 20 mL headspace vial, and 0.1 mL of n-butanol internal standard solution (2000 ppm) was added. After sealing, the vial was incubated in a headspace sampler at 55℃ for 30 min, and after shaking to equilibrate, the sample was injected for analysis. Quantification was performed using the internal standard method. First, standard solutions of different concentrations were prepared using known concentrations of standards and internal standards to establish a calibration curve and obtain the correction factor ratio of each ester to the internal standard. Then, the peak area of ​​each ester in the sample was measured, and the actual concentration (in mg / L) of each ester in the sample was calculated using the established calibration curve.

[0082] Total ester content is calculated using the following formula: Total ester content (mg / L, based on ethyl acetate) = C 乙酸乙酯 + (C 乙酸异戊酯 ×88.11 / 130.19) + (C 己酸乙酯 × 88.11 / 144.21) + (C 辛酸乙酯 × 88.11 / 172.27) + (C 乙酸异丁酯 ×88.11 / 116.16) + (C β-乙酸苯酯 × 88.11 / 164.20), where C 各酯 The values ​​represent the actual concentrations of each ester determined by gas chromatography. The molecular weights of each ester are as follows: ethyl acetate 88.11, isoamyl acetate 130.19, ethyl hexanoate 144.21, ethyl octanoate 172.27, isobutyl acetate 116.16, and β-phenyl acetate 164.20. This calculation method follows the conversion method for each monoester content described in "Questions on the Determination of Total Esters in Baijiu." The content of each ester is divided by its molecular weight, then multiplied by the molecular weight of ethyl acetate. Finally, the converted values ​​of each ester are summed to obtain the total ester content.

[0083] (2) Aroma retention time determination: The beer samples were placed under standard conditions (constant temperature of 25℃, protected from light). Every 3 days, a trained sensory evaluation group (20 people) scored the aroma intensity of the beer samples (0-10 points). The time when the aroma intensity score first fell below 3.0 points was taken as the aroma retention time.

[0084] (3) Sensory evaluation: An evaluation team of 20 trained sensory evaluators will score the aroma richness, taste harmony and overall acceptability of the beer samples (0-10 points) and take the average value.

[0085] The experimental results are shown in Table 1.

[0086] Table 1. Comparison of aroma quality of different sorghum beer samples

[0087] The results in Table 1 show that: Synergistic effect of blended hops: Comparative Example 1 (Gusbruck:Melalon = 60:40), Comparative Example 1 (Gusbruck only), and Comparative Example 2 (Melalon only), with the same total amount of hops used, the total ester content reached 4.85 mg / L when the two hops were used in combination, significantly higher than that of Gusbruck alone (3.12 mg / L) and Melalon alone (3.98 mg / L). This increase (4.85 is significantly higher than the average of 3.55 for 3.12 + 3.98) indicates a significant synergistic effect between the two hops. Regarding aroma retention time, Sample 1, using the blend, achieved an aroma retention time of 21 days, significantly better than Gusbruck alone (14 days) and Melalon alone (16 days). This indicates that the aroma components of the two hops mutually protect and synergistically release within the beer matrix, prolonging aroma persistence. The inventors believe the reason may be that the lower content of geraniol (15-30%) and the higher proportion of sesquiterpenes (humulene, eugenol) in Gusbruck form a slow-release aroma framework, while the exceptionally high content of geraniol (59-65%) and abundant ester precursors in Melaleuca constitute the source of fast-release aroma bursts. During wort boiling and low-temperature fermentation, the two construct a slow-release-protective complex micelle structure through intermolecular π-π stacking or hydrophobic interactions between geraniol and sesquiterpenes. This allows highly volatile esters (such as isoamyl acetate) to be encapsulated by sesquiterpenes, delaying their release, while the oxidative degradation of sesquiterpenes themselves is also inhibited by the presence of esters. This dual protective effect results in a total ester accumulation (4.85 mg / L) and aroma retention time (21 days) that significantly exceed the theoretical summation values ​​when using a single hop (average 3.55 mg / L, 16 days).

[0088] The optimization effect of the blended hop ratio: Comparing Example 1 (60:40), Example 2 (40:60), Example 3 (70:30), and Comparative Example 3 (80:20) and Comparative Example 4 (20:80), when the mass ratio of Cousbrook to Melon was 60:40, the total ester content was the highest (4.85 mg / L), the aroma retention time was the longest (21 days), and the sensory score was also the highest (aroma richness 9.2 points, overall acceptability 9.1 points). When the Cousbrook ratio was too high (80:20) or too low (20:80), the total ester content and sensory score both decreased significantly. When the ratio deviated to 80:20, the aroma richness score dropped to 7.8 points; when the ratio deviated to 20:80, the taste harmony score dropped to 7.9 points. This fully demonstrates that 60:40 is the optimal ratio, at which the aroma components of the two hops achieve the best synergistic balance.

[0089] Aroma Characteristic Analysis: Sensory evaluation results show that the aroma of Comparative Example 1 (Gusbruck only) is mainly floral and herbal, with a relatively simple aroma structure; the aroma of Comparative Example 2 (Micahlon only) is mainly tropical fruit, with a strong aroma impact but lacking in complexity; while the aroma of Example 1 presents a perfect fusion of floral, herbal and tropical fruit aromas, with rich aroma layers, strong three-dimensionality, and the best taste harmony (8.8 points).

[0090] In summary, this invention, by employing a composite hop mixture of Gusbruck and Melon hops at an optimal mass ratio of 60:40, significantly enhances the aroma quality of sorghum beer, achieving a total ester content of 4.85 mg / L and an aroma retention time of 21 days. The sensory evaluation is significantly superior to solutions using either hop alone, demonstrating promising application prospects.

Claims

1. A method for brewing sorghum beer, characterized in that, Includes the following steps: (1) Raw material pretreatment: After crushing the sorghum, mix it with barley malt in a certain proportion, add water for gelatinization treatment, the gelatinization temperature is 95-105℃, and the gelatinization time is 50-70min; (2) Saccharification: The gelatinized mash is saccharified by heating in stages, successively heating to 53-55℃ and holding for 25-35 min, 62-64℃ and holding for 25-35 min, 68-70℃ and holding for 35-45 min, and 77-79℃ and holding for 12-18 min; (3) Filtration: The saccharified wort is pumped into a filter tank for filtration, the first wort is collected, and then the slag is washed and the washed wort is collected. (4) Boiling: Boil the filtered wort at a temperature of 97-98°C for 60-80 minutes. Add compound hops in stages during the boiling process. The compound hops are composed of Gusbruck and Melon in a mass ratio of 40:60-70:

30. (5) Whirlpool sedimentation: The boiled wort is poured into a whirlpool sedimentation tank, allowed to settle and swirl, and then pre-cooled to 16-20°C; (6) Fermentation: Inoculate the cooled wort with yeast for fermentation at a temperature of 11-15°C until the sugar content drops to the target value to obtain sorghum beer.

2. The brewing method according to claim 1, characterized in that, The mass ratio of sorghum to barley malt in step (1) is 20:80 to 40:

60.

3. The brewing method according to claim 1, characterized in that, The total amount of compound hops added in step (4) is 150-300g per ton of wort.

4. The brewing method according to claim 1, characterized in that, The specific operation of adding compound hops in stages as described in step (4) is as follows: add Gusbruck 4 to 6 minutes after the start of boiling, and add Melonlong 13 to 18 minutes before the end of boiling.

5. The brewing method according to claim 1, characterized in that, The heating rate for the segmented heating saccharification in step (2) is 1-2 °C / min.

6. The brewing method according to claim 1, characterized in that, The washing of the lees in step (3) is carried out in 3 times, with the washing water temperature being 76-80℃ and the total washing water volume being 0.8-1.2 times the volume of wort.

7. The brewing method according to claim 1, characterized in that, The vortex precipitation time in step (5) is 20 to 40 minutes, and the cooling flow rate of the pre-cooling is 80 to 120 L / min.

8. The brewing method according to claim 1, characterized in that, The yeast mentioned in step (6) is Lager yeast, and the inoculation amount is 0.5 to 1.0 kg per ton of wort.

9. The brewing method according to claim 1, characterized in that, The fermentation described in step (6) includes primary fermentation and secondary fermentation. The primary fermentation temperature is 11-14°C. After fermentation, the sugar content drops to below 4.0°P, the container is sealed and pressurized. The secondary fermentation temperature is 12-14°C. The fermentation is carried out under pressure until the sugar content drops to below 3.5°P.

10. Sorghum beer prepared by the brewing method according to any one of claims 1 to 9.

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