Preparation method of long-acting fresh original beer with stable taste

Abstract

The invention relates to the technical field of beer brewing, and particularly discloses a preparation method of long-acting fresh stable-taste original beer, which comprises the following steps: raw material pretreatment, saccharification and filtration, boiling and hops addition, cooling and oxygenation, fermentation, dry addition of hops and after-ripening. Wherein the raw materials comprise Pearson malt, wheat malt, burnt crystal malt and malt with an antioxidant function in a weight ratio of (70-85): (5-15): (5-10): (0.5-5); the fermentation method comprises the following steps: inoculating saccharomycetes into wort for fermentation, and then heating for diacetyl reduction; the step of dry addition of hops comprises the following steps: adding fragrant flower type hops into a fermentation system, and extracting for 3-5 days; and after the extraction is finished, adding modified konjac glucomannan, uniformly stirring and standing. According to the preparation method of the original pulp beer, the problems that traditional original pulp beer is prone to oxidation, unstable in flavor, large in colloidal precipitate amount, rapid in taste deterioration and the like can be solved, and long-term stability of the fresh taste of the original pulp beer is achieved.

Description

Technical Field

[0001] This application relates to the field of beer brewing technology, specifically to a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor. Background Technology

[0002] Unpasteurized beer, made with an all-malt blend and brewed without filtration or pasteurization, retains its natural nutrients and vibrant flavor to the greatest extent possible, making it a favorite among consumers. However, this very brewing process also leads to serious taste degradation issues in traditional unpasteurized beer, specifically: 1. Some malts commonly used in traditional unpasteurized beer (such as dark roasted malts and some base malts) contain high levels of unsaturated fatty acids and polyphenols. These substances are precursors to oxidation reactions and are prone to oxidation during storage and consumption, resulting in a "stale" taste, characterized by cardboard and astringency, severely impacting the drinking experience. 2. To achieve a rich aroma, traditional brewing methods heavily rely on late-boiling or dry-hopping hops. However, some hop varieties have high polyphenol content, and improper addition can cause a large amount of easily oxidized hop oils to dissolve, not only failing to maintain flavor stability but also exacerbating oxidation, leading to rapid aroma decay and a deteriorated taste. Third, during fermentation, yeast produces a certain amount of higher alcohols, diacetyl, and other substances. If not properly controlled, the residues or subsequent transformations of these substances will damage the purity and stability of the taste. At the same time, yeast autolysis will release substances that cause beer to become cloudy and produce off-flavors, further affecting product quality.

[0003] To address the aforementioned issues, existing technologies mostly employ methods such as adding artificial antioxidants and optimizing filtration processes. However, the addition of artificial antioxidants can affect the natural properties of unpasteurized beer, while the enhancement of filtration processes can result in the loss of some fresh flavor. Neither of these methods can fundamentally solve the core needs of stable taste and long-lasting freshness in unpasteurized beer.

[0004] Therefore, developing a formula and brewing method that does not destroy the natural characteristics of unpasteurized beer, and can inhibit oxidation and precipitation from the source and maintain a long-lasting fresh taste has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In order to overcome the problem of easy deterioration of taste in existing unpasteurized beer brewing methods, this application provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0006] This application provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor, using the following technical solution: A method for preparing unpasteurized beer with a long-lasting fresh taste includes the following steps: raw material pretreatment, saccharification and filtration, boiling and hop addition, cooling and oxygenation, fermentation, dry hop addition and post-maturation; The raw materials comprise Pilsner malt, wheat malt, caramel crystal malt, and antioxidant malt in a weight ratio of (70-85):(5-15):(5-10):(0.5-5); the antioxidant malt is buckwheat malt or oat malt. The fermentation steps are as follows: yeast is inoculated into wort for fermentation, and then the temperature is raised to reduce diacetyl; on the third day of fermentation, enzymatically modified yeast glucan is added to the fermentation system and stirred evenly; immediately after raising the temperature, half of the amount of γ-polyglutamic acid is added to the fermentation product, and the remaining γ-polyglutamic acid is added after an interval of 12-18 hours. The amount of enzyme-modified yeast glucan added is 150-200 mg / L based on the volume of wort, and the amount of γ-polyglutamic acid added is 80-120 mg / L. The dry hopping step is as follows: add aromatic hops to the fermentation system and extract for 3-5 days; after extraction, add modified konjac glucomannan, stir well and let stand. The amount of modified konjac glucomannan added is 100-150 mg / L based on the volume of wort.

[0007] This application provides a method for preparing unpasteurized beer. This method, through raw material selection and formulation optimization, as well as the coordination of adjuncts during fermentation and dry hopping, overcomes the shortcomings of traditional unpasteurized beer, such as easy oxidation, unstable flavor, excessive colloidal sedimentation, and rapid taste deterioration, while retaining the characteristics of unpasteurized beer: whole malt, no filtration, and no pasteurization. This achieves long-term stability of the fresh taste of unpasteurized beer. Specifically, this application uses Pilsner malt as the base malt, and by combining it with a specific ratio of wheat malt, caramel crystal malt, and antioxidant malt, it not only ensures the basic flavor of the unpasteurized beer but also enhances its free radical resistance from the source, delaying the oxidative deterioration of the beer. Secondly, during the fermentation stage, by adding enzymatically modified yeast glucomannan on the third day, its water solubility and molecular structure protect the integrity of the yeast cell membrane, inhibit autolysis, and reduce the release of intracellular off-flavor substances. Furthermore, it can adsorb metabolic impurities such as higher alcohols, reducing the risk of subsequent taste deterioration. The addition of γ-polyglutamic acid can efficiently enhance reductase activity during the diacetyl reduction period, accelerating diacetyl degradation and complexing residual off-flavor substances, preventing the formation of a "stale food" taste. Additionally, by adding modified konjac glucomannan after dry hopping, a network flocculation structure can be formed, efficiently adsorbing suspended yeast cells and autolysis fragments, significantly improving sedimentation efficiency and reducing yeast residue in the finished product. In summary, this application, through the synergistic effect of the aforementioned specific malt formula and three types of adjuvants, not only preserves the natural attributes of unfiltered and unpasteurized beer, but also significantly extends the fresh taste and shelf life of beer through antioxidant protection and off-flavor degradation, resulting in a smooth, pure taste without impurities, and greatly optimized turbidity and stability indicators, thus achieving a comprehensive improvement in beer flavor, freshness, and shelf life.

[0008] Optionally, the weight ratio of the Pilsner malt, wheat malt, caramel crystal malt, and antioxidant malt is 80:10:8:2.

[0009] Optionally, the floral hops are selected from Cascade and Sichu.

[0010] Optionally, in the fermentation step, the inoculum size of yeast is 1.0 × 10⁻⁶. 6 The fermentation temperature is 8-9℃ and the fermentation time is 7-8 days; the diacetyl reduction temperature is 12-13℃ and the time is 2-3 days, and the diacetyl content after diacetyl reduction is ≤0.05mg / L.

[0011] Optionally, the boiling and hop addition steps are as follows: heating the wort mash obtained from saccharification and filtration, adding bitter hops at 5-10 minutes of boiling, adding silica gel at 25-35 minutes of boiling, and adding aroma-stabilizing hops at 85-90 minutes of boiling; after boiling for 100 minutes, adding lactic acid to adjust the pH, followed by vortex precipitation and cooling to obtain clear wort.

[0012] Optionally, the bittering hops are Magnum, and the aroma-stabilizing hops are Saaz; the amount of silica gel added is 10g / 100L based on the volume of wort.

[0013] Optionally, in the cooling and oxygenation steps, the dissolved oxygen in the wort is adjusted to 8-10 mg / L; in the fermentation steps, CO2 needs to be pre-filled to replace the oxygen content in the fermenter to ≤0.5%.

[0014] Optionally, the saccharification and filtration steps are as follows: water is added to the malt powder at a material-to-water ratio of 1:(4-5), the temperature is raised to 35-38℃ and kept at that temperature for 10-20 minutes, then the temperature is raised to 45-48℃ and kept at that temperature for 30-35 minutes, then the temperature is raised to 62-64℃ and kept at that temperature for 50-60 minutes, then the temperature is raised to 67-68℃ and kept at that temperature for 30-40 minutes, and finally the temperature is raised to 76-78℃ and kept at that temperature for 10-15 minutes to terminate the saccharification; after standing for 30 minutes, the mixture is filtered to obtain the wort saccharified liquid.

[0015] Secondly, this application provides a long-lasting, fresh, and stable-tasting unpasteurized beer, brewed using the aforementioned preparation method.

[0016] In summary, this application has the following beneficial effects: 1. This application provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor. It uses Pilsner malt, which is low in protein and low in polyphenols, as the base malt. By combining it with wheat malt, caramel crystal malt, and antioxidant functional malt, it reduces oxidation precursors and inhibits oxidation reactions from the source, so that the unpasteurized beer is free of cardboard taste and astringency, and greatly extends the shelf life of fresh taste.

[0017] 2. This application uses enzymatically modified yeast glucan and γ-polyglutamic acid in the fermentation step and modified konjac glucomannan in the dry hopping step, which can further avoid problems such as beer oxidation, off-flavor release, and taste deterioration, thereby obtaining a long-term stable unpasteurized beer with a fresh taste.

[0018] 3. The preparation method provided in this application does not add artificial antioxidants, does not use enhanced filtration or pasteurization processes, and fully preserves the natural attributes of unpasteurized beer: "all malt, unfiltered, and unpasteurized," resulting in minimal loss of nutrients and a prominent fresh flavor. Attached Figure Description

[0019] Figure 1 This is a flowchart of the preparation method of long-lasting fresh and stable-tasting unpasteurized beer provided in this application. Detailed Implementation

[0020] This application provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor, comprising the following steps: (1) Raw material pretreatment: Pilsner malt, wheat malt, caramel crystal malt and antioxidant malt were weighed according to the weight ratio of (70-85): (5-15): (5-10): (0.5-5), and then mixed and pulverized to obtain malt powder; (2) Saccharification and filtration: Add brewing water to the malt powder at a material-to-water ratio of 1:(4-5), heat to 35-38℃, keep warm for 10-20 min, then heat to 45-48℃, keep warm for 30-35 min, then heat to 62-64℃, keep warm for 50-60 min, continue to heat to 67-68℃, keep warm for 30-40 min, and finally heat to 76-78℃, keep warm for 10-15 min to terminate saccharification. Control the soluble protein content of the wort saccharification liquid to ≤4.5 mg / mL; after standing for 30 min, filter to obtain a wort saccharification liquid with a turbidity ≤5 NTU. (3) Boiling and hop addition: Heat the wort mash, add bitter hops at 5-10 min of boiling, add food-grade silica gel at 25-35 min of boiling, and add aroma-stabilizing hops at 85-90 min of boiling; after boiling for 100 min, add lactic acid to adjust the pH of the wort to 5.0-5.4, and obtain a clear wort with turbidity ≤2 NTU by vortex precipitation and cooling. (4) Cooling and oxygenation: The wort is rapidly cooled to 8-9°C using a plate heat exchanger for ≤40 minutes. Sterile air is introduced to control the dissolved oxygen in the wort to 8-10 mg / L, and then it is transferred to a fermentation tank.

[0021] (5) Fermentation: Sterilize the fermentation tank with 85℃ hot water for 30 minutes in advance, cool it, and then purge it with CO2 2-4 times to make the oxygen content in the tank ≤0.5%; add yeast at 1.0×10 6 Inoculate the wort with an inoculum of 1 / mL and ferment at 8-9℃ for 7 days; then raise the temperature to 12-13℃ for diacetyl reduction for 2-3 days until the diacetyl content is ≤0.05mg / L; On the third day of fermentation, enzyme-modified yeast glucan was added to the fermentation system and stirred evenly. After the temperature was raised to 12-13℃, half of the amount of γ-polyglutamic acid was added to the fermentation product, and the remaining γ-polyglutamic acid was added after an interval of 12-18 hours. The amount of enzymatically modified yeast glucan added is 150-200 mg / L based on the volume of wort. Before use, it is diluted with sterile water to a concentration of 2-3 g / 100 mL. The amount of γ-polyglutamic acid added is 80-120 mg / L. Before use, it is diluted with sterile water to a concentration of 1-2 g / 100 mL.

[0022] (6) Dry hop addition: Pass CO2 with a purity of ≥99.99% into the fermentation tank 2-4 times for replacement, then quickly add aromatic hops, continue to pass CO2 for 5-10 minutes, and extract at 10-12℃ and 0.1-0.12MPa for 3-5 days, stirring 1-2 times a day for 5-10 minutes each time; after extraction, add modified konjac glucomannan, stir for 20-30 minutes, and then let stand for 12-16 hours. The amount of modified konjac glucomannan added is 100-150 mg / L based on the volume of wort. When using it, add sterile water and ultrasonically disperse it into a modified konjac glucomannan solution with a concentration of 1-2 g / 100 mL.

[0023] (7) Post-fermentation: After standing, the temperature is reduced to 0-2℃ at a rate of 0.5-1℃ / h and kept warm for 10-12 days. Chitosan is added on the 7th day at a rate of 5mg / 100mL. After the warming period, the temperature is reduced to obtain unpasteurized beer.

[0024] In this application, Pilsner malt has a protein content ≤9.5%, a polyphenol content ≤1.2%, and a color EBC ≤10; wheat malt has a moisture content ≤10% and a protein content of 8.5-9.0%; caramel crystal malt has a color EBC ≤50; buckwheat malt has a flavonoid content ≥0.8% and a ferulic acid content ≥0.15%; yeast glucan has a CAS number of 9012-72-0; konjac glucomannan has a CAS number of 37220-17-0; γ-polyglutamic acid was purchased from Shanghai Zhongfeng Biotechnology Co., Ltd.; all raw materials, reagents, solvents, etc. used in this application are commercially available.

[0025] The present application will be further described in detail below with reference to preparation examples, embodiments, performance testing tests and accompanying drawings. Preparation Example 1

[0026] Preparation Example 1 provides an enzymatically modified yeast glucan.

[0027] The preparation method of the above-mentioned enzymatically modified yeast glucan is as follows: 100g of yeast glucan is added to sterile water to prepare a 10% suspension. The pH is adjusted to 5.5, and then the temperature is raised to 50±5℃ and kept at this temperature for 30min. Then, 0.6g of β-1,3-glucanase is added and the mixture is stirred for 5h of enzymatic hydrolysis until the molecular weight of the glucan reaches 40kDa, at which point the enzymatic hydrolysis is terminated. The solution is then heated to 90±5℃ and kept at this temperature for 20min to completely inactivate the β-1,3-glucanase. After cooling to below 40℃, the solution is centrifuged and the supernatant is collected. Finally, 95% food-grade ethanol is added to the supernatant, stirred evenly, and allowed to stand for 24h. The precipitate is collected and washed twice with 70% ethanol and once with sterile water. Finally, the precipitate is concentrated, dried, and pulverized to obtain the enzymatically modified yeast glucan. Preparation Example 2

[0028] Preparation Example 2 provides a modified konjac glucomannan.

[0029] The preparation method of the above-mentioned modified konjac glucomannan includes the following steps: (1) Add 1L of 20% ethanol solution to 100g of konjac glucomannan at a stirring rate of 40r / min, stir at room temperature for 20min, centrifuge and take the supernatant to obtain konjac glucomannan suspension; (2) Heat the konjac glucomannan suspension to 85°C and gelatinize for 15 min to form a transparent viscous liquid. Slowly cool down to 55°C. Then add 10wt% citric acid solution to the gelatinized liquid, stir evenly, and adjust the pH of the system to 5.7. Then add 0.3g of β-mannanase, stir continuously for enzymatic hydrolysis, and use a rotational viscometer (25°C, rotor No. 6, 60r / min) to detect the viscosity. When the viscosity drops to 180±20mPa·s, immediately raise the temperature to 90°C and keep warm for 15 min to completely inactivate the enzyme.

[0030] (3) Cool the enzymatic hydrolysate to 40°C, centrifuge and take the supernatant; finally add 95% food grade ethanol to the supernatant, stir evenly and let stand for 24 hours, collect the precipitate, wash the precipitate twice with 70% ethanol and once with sterile water; finally concentrate, dry and pulverize the precipitate to obtain modified konjac glucomannan. Example 1

[0031] Example 1 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor, comprising the following steps: (1) Raw material pretreatment: Weigh Pilsner malt, wheat malt, crystal malt and buckwheat malt in a weight ratio of 80:10:8:2, then mix and grind them to obtain malt powder; (2) Saccharification and filtration: Add 100 kg of malt powder and 400 kg of brewing water to the saccharification pot, raise the temperature to 37°C, keep it at 15 min, then raise the temperature to 47°C, keep it at 32 min, then raise the temperature to 63°C, keep it at 60 min, continue to raise the temperature to 68°C, keep it at 30 min, and finally raise the temperature to 77°C, keep it at 10 min to terminate saccharification. Control the soluble protein content of the wort saccharification liquid to ≤4.5 mg / mL; after standing for 30 min, filter to obtain a wort saccharification liquid with a turbidity ≤5 NTU. (3) Boiling and hop addition: Heat the wort mash, add Magnum hops at 7 min of boiling, add food-grade silica gel at 30 min of boiling, and add Saaz hops at 90 min of boiling; after boiling for 100 min, add lactic acid to adjust the pH of the wort to 5.2, and obtain a clear wort with turbidity ≤2 NTU by vortex precipitation and cooling. (4) Cooling and oxygenation: The wort is rapidly cooled to 8°C using a plate heat exchanger for 30 minutes. Sterile air is introduced to control the dissolved oxygen in the wort to 10 mg / L, and then it is transferred to a fermentation tank.

[0032] (5) Fermentation: Sterilize the fermentation tank with 85℃ hot water for 30 minutes in advance, cool it, and then purge it with CO2 three times to ensure that the oxygen content in the tank is ≤0.5%; add yeast at a rate of 1.0×10 6 Inoculate the wort at an inoculum rate of 1 inoculum per mL and ferment at 8°C for 7 days; then raise the temperature to 12°C for diacetyl reduction for 3 days until the diacetyl content is ≤0.05 mg / L; On the third day of fermentation, enzyme-modified yeast glucan was added to the fermentation system and stirred evenly. After the temperature was raised to 12-13℃, half of the amount of γ-polyglutamic acid was added to the fermentation product, and the remaining γ-polyglutamic acid was added after an interval of 12-18 hours. The amount of enzymatically modified yeast glucan added is 180 mg / L based on the volume of wort. Before use, it is diluted with sterile water to a concentration of 3 g / 100 mL. The amount of γ-polyglutamic acid added is 100 mg / L. Before use, it is diluted with sterile water to a concentration of 1.5 g / 100 mL.

[0033] (6) Dry hop addition: CO2 with a purity of ≥99.99% is introduced into the fermentation tank three times for replacement, then Cascade hops are quickly added, CO2 is continued to be introduced for 10 min, and the mixture is extracted at 12℃ and 0.1MPa for 4 days, with stirring once a day for 10 min each time; after the extraction is completed, modified konjac glucomannan is added, stirred for 30 min, and then allowed to stand for 14 h. The modified konjac glucomannan was added at a rate of 130 mg / L based on the volume of wort. When using it, it was added to sterile water and ultrasonically dispersed to form a modified konjac glucomannan solution with a concentration of 1.5 g / 100 mL.

[0034] (7) Post-fermentation: After the settling period, the temperature is reduced to 2°C at a rate of 0.5°C / h and kept warm for 12 days. Chitosan is added on the 7th day at a rate of 5mg / 100mL. After the warming period, the temperature is reduced to obtain unpasteurized beer. Example 2

[0035] Example 2 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0036] The difference between the above embodiment and Embodiment 1 is that the weight ratio of Pilsner malt, wheat malt, caramel crystal malt and buckwheat malt is 70:15:10:5. Example 3

[0037] Example 3 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0038] The difference between the above embodiment and Embodiment 1 is that the weight ratio of Pilsner malt, wheat malt, caramel crystal malt and buckwheat malt is 85:5:5:5. Example 4

[0039] Example 4 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0040] The difference between the above embodiment and Embodiment 1 is that the weight ratio of Pilsner malt, wheat malt, caramel crystal malt and buckwheat malt is 79:10:10:1. Example 5

[0041] Example 5 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0042] The difference between the above embodiment and Example 1 is that the amount of enzyme-modified yeast glucan added in the fermentation step is 150 mg / L. Example 6

[0043] Example 6 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0044] The difference between the above embodiment and Example 1 is that the amount of enzyme-modified yeast glucan added in the fermentation step is 200 mg / L. Example 7

[0045] Example 7 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0046] The difference between the above embodiment and Example 1 is that the amount of γ-polyglutamic acid added in the fermentation step is 80 mg / L. Example 8

[0047] Example 8 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0048] The difference between the above embodiment and Example 1 is that the amount of γ-polyglutamic acid added in the fermentation step is 120 mg / L. Example 9

[0049] Example 9 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0050] The difference between the above embodiment and Embodiment 1 is that the amount of modified konjac glucomannan added in the dry hopping step is 100 mg / L. Example 10

[0051] Example 10 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0052] The difference between the above embodiment and Embodiment 1 is that the amount of modified konjac glucomannan added in the dry hopping step is 150 mg / L. Comparative Example 1

[0053] Comparative Example 1 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0054] The difference between the above comparative example and Example 1 is that the raw materials used are Pilsner malt, wheat malt and caramel crystal malt in a weight ratio of 80:10:10. Comparative Example 2

[0055] Comparative Example 2 provides a method for preparing unpasteurized beer with a long-lasting fresh taste.

[0056] The difference between the above comparative example and Example 1 is that the raw materials used are Pilsner malt, wheat malt and buckwheat malt in a weight ratio of 80:10:10. Comparative Example 3

[0057] Comparative Example 3 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0058] The difference between the above comparative example and Example 1 is that the raw materials used are Pilsner malt and wheat malt in a weight ratio of 80:20. Comparative Example 4

[0059] Comparative Example 4 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0060] The difference between the above comparative example and Example 1 is that: no enzymatically modified yeast glucan and γ-polyglutamic acid were added during the fermentation step; and no modified konjac glucomannan was added during the dry hopping step. Specifically: (5) Fermentation: Sterilize the fermentation tank with 85℃ hot water for 30 minutes in advance, cool it, and then purge it with CO2 three times to ensure that the oxygen content in the tank is ≤0.5%; add yeast at a rate of 1.0×10 6 Inoculate the wort at an inoculum rate of 1 inoculum per mL and ferment at 8°C for 7 days; then raise the temperature to 12°C for diacetyl reduction for 3 days until the diacetyl content is ≤0.05 mg / L.

[0061] (6) Dry hop addition: Pass CO2 with a purity of ≥99.99% into the fermentation tank three times until the oxygen content in the tank is ≤0.1%. Then quickly add Cascade hops, continue to pass CO2 for 10 minutes, and extract at 12℃ and 0.1MPa for 4 days, stirring once a day for 10 minutes each time. Comparative Example 5

[0062] Comparative Example 5 provides a method for preparing unpasteurized beer with a long-lasting fresh taste.

[0063] The difference between the above comparative example and Example 1 is that: in the fermentation step, the amount of enzyme-modified yeast glucan added is 100 mg / L, the amount of γ-polyglutamic acid added is 50 mg / L, and in the dry hopping step, the amount of modified konjac glucomannan added is 50 mg / L. Comparative Example 6

[0064] Comparative Example 6 provides a method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor.

[0065] The difference between the above comparative example and Example 1 is that: in the fermentation step, the amount of enzyme-modified yeast glucan added is 250 mg / L, the amount of γ-polyglutamic acid added is 150 mg / L, and in the dry hopping step, the amount of modified konjac glucomannan added is 200 mg / L. Performance testing

[0066] Unpasteurized beer was prepared according to the methods of Examples 1-10 and Comparative Examples 1-5. Unpasteurized beer stored at room temperature for 0 days (initial), 1 month, and 6 months was used as test objects, and various tests were performed. The results are shown in Table 2 below.

[0067] (1) Detection of trans-2-nonenal content: The main representative substance of aging flavor in beer is trans-2-nonenal (cardboard flavor), and its content can be used as the main indicator for evaluating the aging flavor of beer. The detection method is based on the "Determination of trace trans-2-nonenal in beer by SPE-HPLC" (DOI: CNKI:SUN:SPKJ.0.2008-05-088).

[0068] (2) Sensory evaluation: A sensory evaluation group consisting of 10 sensory evaluation members (aged 20-55, 5 males and 5 females) will be formed. The evaluators will score each test object according to the scoring criteria shown in Table 1. Each member will evaluate each sample 3 times. Finally, the average score of the same sample will be taken as the final sensory evaluation score of each group.

[0069] Table 1 Sensory Evaluation Criteria

[0070] Table 2 Performance test results of unpasteurized beer obtained in Examples 1-10 and Comparative Examples 1-5

[0071] According to the test results in Table 2, the initial trans-2-nonenal content of the unpolished beer obtained by the preparation methods provided in Examples 1-10 was 0.3-0.6 μg / L, with a sensory score of 36.6-38.6; after being stored at room temperature for 1 month, the trans-2-nonenal content was 0.3-0.7 μg / L, with a sensory score of 35.1-37.4; and after being stored at room temperature for 6 months, the trans-2-nonenal content was 0.7-1.5 μg / L, with a sensory score of 30.5-36. The initial trans-2-nonenal content of the unpasteurized beer prepared by the methods provided in Comparative Examples 1-5 was 0.4-0.7 μg / L, with a sensory score of 34.9-36.5. After being stored at room temperature for one month, the trans-2-nonenal content was as high as 0.8-1.6 μg / L, with a sensory score of only 30.4-31.3. After being stored at room temperature for six months, the trans-2-nonenal content was as high as 1.1-3.4 μg / L, with a sensory score of only 20.2-26.2. Therefore, this application uses Pilsner malt, wheat malt, caramel crystal malt and antioxidant functional malt in a weight ratio of (70-85):(5-15):(5-10):(0.5-5) as raw materials. By using enzymatically modified yeast glucan and γ-polyglutamic acid in the fermentation step and modified konjac glucomannan in the dry hopping step, it is possible to avoid problems such as beer oxidation, unstable flavor and deterioration of taste, and obtain a long-term stable unpasteurized beer with a fresh taste.

[0072] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing unpasteurized beer with a long-lasting fresh taste and stable flavor, characterized in that, Includes the following steps: Raw material pretreatment, saccharification and filtration, boiling and hop addition, cooling and oxygenation, fermentation, dry hopping and aging; The raw materials comprise Pilsner malt, wheat malt, caramel crystal malt, and antioxidant malt in a weight ratio of (70-85):(5-15):(5-10):(0.5-5); the antioxidant malt is buckwheat malt or oat malt. The fermentation steps are as follows: yeast is inoculated into wort for fermentation, and then the temperature is raised to reduce diacetyl; on the third day of fermentation, enzymatically modified yeast glucan is added to the fermentation system and stirred evenly; immediately after raising the temperature, half of the amount of γ-polyglutamic acid is added to the fermentation product, and the remaining γ-polyglutamic acid is added after an interval of 12-18 hours. The amount of enzyme-modified yeast glucan added is 150-200 mg / L based on the volume of wort, and the amount of γ-polyglutamic acid added is 80-120 mg / L. The dry hopping step is as follows: add aromatic hops to the fermentation system and extract for 3-5 days; after extraction, add modified konjac glucomannan, stir evenly and let stand. The amount of modified konjac glucomannan added is 100-150 mg / L based on the volume of wort.

2. The preparation method according to claim 1, characterized in that, The weight ratio of Pilsner malt, wheat malt, caramel crystal malt, and antioxidant malt is 80:10:8:

2.

3. The preparation method according to claim 1, characterized in that, The aromatic hops are selected from Cascade and West Chu.

4. The preparation method according to claim 1, characterized in that, In the fermentation step, the inoculum size of yeast is 1.0 × 10⁻⁶. 6 The fermentation temperature is 8-9℃ and the fermentation time is 7-8 days; the diacetyl reduction temperature is 12-13℃ and the time is 2-3 days, and the diacetyl content after diacetyl reduction is ≤0.05mg / L.

5. The preparation method according to claim 1, characterized in that, The boiling and hop addition steps are as follows: the wort mash obtained from saccharification and filtration is heated, bitter hops are added at 5-10 minutes of boiling, silica gel is added at 25-35 minutes of boiling, and aroma-stabilizing hops are added at 85-90 minutes of boiling; after boiling for 100 minutes, lactic acid is added to adjust the pH, and after vortex precipitation and cooling, clear wort is obtained.

6. The preparation method according to claim 5, characterized in that, The bittering hops are Magnum, and the aroma-stabilizing hops are Saaz; the amount of silica gel added is 10g / 100L by the volume of wort.

7. The preparation method according to claim 1, characterized in that, In the cooling and oxygenation steps, the dissolved oxygen in the wort is adjusted to 8-10 mg / L; in the fermentation step, CO2 needs to be pre-filled to replace the oxygen content in the fermenter to ≤0.5%.

8. The preparation method according to claim 1, characterized in that, The saccharification and filtration steps are as follows: water is added to the malt powder at a material-to-water ratio of 1:(4-5), the temperature is raised to 35-38℃ and kept at that temperature for 10-20 minutes, then the temperature is raised to 45-48℃ and kept at that temperature for 30-35 minutes, then the temperature is raised to 62-64℃ and kept at that temperature for 50-60 minutes, then the temperature is raised to 67-68℃ and kept at that temperature for 30-40 minutes, and finally the temperature is raised to 76-78℃ and kept at that temperature for 10-15 minutes to terminate the saccharification; after standing for 30 minutes, the mixture is filtered to obtain the wort saccharified liquid.

9. A long-lasting, fresh, and stable unpasteurized beer, characterized in that, It is brewed using the preparation method described in any one of claims 1-8.

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