A low purine beer and a method for preparing the same

Abstract

This application relates to the field of beer preparation technology, specifically disclosing a low-purine beer and its preparation method. The method for preparing a low-purine beer is as follows: malt is crushed and sieved, mixed with water, heated for saccharification, filtered, and the lees are washed to obtain a first wort and lees; the first wort is boiled, hops are added before the boiling is finished, cooled, swirl to settle, and then filtered to obtain a second wort; beer yeast is added to the second wort for fermentation to obtain a beer fermentation liquid; an adsorbent is added to the beer fermentation liquid for adsorption, filtered, centrifuged, and sterilized to obtain the final product. The adsorbent includes modified lees, and the raw materials for the modified lees include the lees from step S1, citric acid, and zinc salt. The low-purine beer of this application has a low purine content, making it healthier, while also possessing a rich taste, flavor, and foam performance.

Description

Technical Field

[0001] This application relates to the field of beer preparation technology, and more specifically, to a low-purine beer and a method for preparing the same. Background Technology

[0002] Beer, a fermented beverage with a long history and unique flavor, is loved by consumers all over the world. Its traditional brewing process relies on the fermentation of barley malt, hops and yeast. It is brewed through processes such as malting, saccharification and fermentation, resulting in a refreshing taste, rich foam and unique malty flavor, which occupies an important place in social and leisure scenarios.

[0003] However, due to the extensive use of malt in the beer brewing process, beer contains a relatively high amount of purines. These substances are ultimately metabolized into uric acid in the human body. The alcohol in beer can easily cause lactic acid to accumulate in the body. Once the blood alcohol concentration reaches 200 mg / dL, the lactic acid in the blood will increase with the oxidation of ethanol, which will hinder the excretion of uric acid by the kidneys, disrupt the original balance, and lead to an increase in the uric acid content in the human blood. The uric acid will precipitate in the form of sodium salts, easily forming stones or triggering gout. In severe cases, it can cause red bumps all over the skin, persistent pain and itching, and inability to walk, posing a health risk.

[0004] There is an urgent market demand for low-purine beer. Existing technologies typically reduce purine content by selecting low-purine raw materials, pre-treating raw materials, optimizing production processes, and employing methods such as adsorption, membrane filtration, and enzymatic hydrolysis after brewing. However, the inventors have found that these methods often significantly affect the beer's foaming properties and flavor, and are mostly complex and costly, making large-scale application in production difficult. Therefore, how to reduce beer purine content to make it healthier while maintaining excellent foaming properties and a rich taste, preserving the beer's unique flavor, and meeting consumers' expectations for healthy beer has become a pressing problem for those in the field. Summary of the Invention

[0005] In order to reduce the purine content in traditional beer and enhance its unique flavor and taste, this application provides a low-purine beer and its preparation method.

[0006] In a first aspect, this application provides a method for preparing low-purine beer, employing the following technical solution:

[0007] A method for preparing low-purine beer includes the following steps:

[0008] S1: After crushing the malt and sieving it, add water and mix evenly, then heat it to saccharify. After filtering and washing the malt, the first wort and malt residue are obtained.

[0009] S2: Boil the first wort, add hops before the boiling is finished, cool, swirl to settle, and then filter to obtain the second wort; S3: Add brewer's yeast to the second wort to ferment and obtain beer fermentation liquid;

[0010] S4: Add an adsorbent to the beer fermentation liquid for adsorption, filter, centrifuge, and sterilize to obtain the product. The adsorbent includes modified malt grains, and the raw materials of the modified malt grains include the malt grains from step S1, citric acid, and zinc salt.

[0011] By adopting the above technical solution, using malt residue, a byproduct of saccharification in the beer brewing process, as raw material, not only is waste resource utilization achieved, but production costs are also greatly reduced. Malt residue and beer fermentation liquid have homology in components, including proteins, polysaccharides, and flavor precursors such as esters, higher alcohols, phenolic acids, and aldehydes in malt. This avoids introducing heterogeneous impurities. When used as a purine adsorbent carrier, its surface chemical environment is highly compatible with beer compared to other adsorbent carriers, effectively preventing non-specific adsorption and destruction of foam-related proteins and beer flavor substances in beer, preventing denaturation of foam proteins in beer, and ensuring that beer maintains its excellent foam stability and unique taste and flavor.

[0012] The inventors selectively adsorbed purines by synergistic modification of citric acid and zinc salt to form coordination adsorption sites. The carboxyl group of citric acid and the hydroxyl group of wheat cellulose are esterified to introduce a large number of carboxyl groups on the surface of wheat cellulose. The lone pair electrons of the oxygen atom in the carboxyl group can strongly chelate with the empty orbitals of the divalent zinc ions in the zinc salt to form a coordination structure. Purine is a nitrogen-containing heterocyclic compound, and the N7 site in its molecule can further coordinate with zinc ions to form a stable coordination complex of carboxyl-zinc ion-purine, thereby achieving specific capture of purines without adsorbing foam proteins and flavor molecules that are key to beer foam performance.

[0013] In addition, the adsorbent of this application has the characteristics of environmentally friendly, inexpensive and readily available raw materials and high safety. It has no harmful residues and is healthier. The adsorption step is carried out after fermentation, which also avoids interfering with the flavor substances produced by fermentation metabolism. The process is simple and controllable, suitable for large-scale production, and effectively improves the problem that existing technologies cannot guarantee that the taste and flavor of beer are not lost and the foam performance is not damaged while reducing purines.

[0014] Optionally, the amount of adsorbent added to the beer fermentation broth is 8-15 g / L, and the adsorption time is 50-60 min.

[0015] By adopting the above technical solution, if the amount of adsorbent added is too low, the adsorption of purines may be insufficient and the goal of low purines may not be achieved. If the amount added is too high, it may have an adverse effect on the adsorption effect and may also adsorb flavor substances and foam proteins in beer, ruining the taste. If the adsorption time is too long, impurities may be precipitated due to the sedimentation of the adsorbent, affecting the clarity.

[0016] Optionally, the preparation method of modified wheat lees includes the following steps:

[0017] After freeze-drying the wheat lees from step S1, the lees powder is obtained by pulverizing. Then, it is added to a citric acid solution containing 20-50 g / L of citric acid and 5-10 g / L of esterification reaction catalyst. The esterification reaction is carried out at 150-160℃. After cooling, the mixture is filtered, washed until neutral, dried, and pulverized to obtain acidified wheat lees.

[0018] Add acidified wheat lees to a 0.1-0.3 mol / L zinc salt solution, adjust the pH to 5.5±0.5, shake at 40-60℃ for 2-3 hours, filter, wash and dry to obtain modified wheat lees.

[0019] Optionally, the esterification catalyst is sodium hypophosphite.

[0020] Optionally, the zinc salt is selected from either zinc chloride or zinc sulfate.

[0021] By adopting the above technical solutions, zinc chloride and zinc sulfate are used as zinc salts with higher safety. The process of introducing carboxyl groups through esterification and then coordinating zinc ions significantly improves the purine adsorption capacity of wheat lees, significantly improves the problems of poor adsorption specificity and easy destruction of beer flavor of traditional adsorbents, the process parameters are clear, the modification effect is stable, and it is suitable for large-scale development.

[0022] Optionally, the wheat lees powder may undergo the following pretreatment before being added to the citric acid solution:

[0023] The wheat lees powder was steam-exploded, then added to sodium citrate-citric acid buffer solution, and 3-4% of the weight of the wheat lees powder was added to the compound enzyme for enzymatic hydrolysis. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees.

[0024] Add the enzymatically hydrolyzed wheat lees to water at 75-85℃, stir and centrifuge, then add water at 50-60℃, stir and centrifuge again, and finally wash, filter, dry and crush with water at 25-30℃ to obtain pretreated wheat lees.

[0025] Optionally, the complex enzyme comprises nuclease, cellulase and xylanase in a mass ratio of (3-4):(1-2):1.

[0026] By employing the above technical solution, the wheat residue is pretreated to remove residual purine substances, preventing a decrease in subsequent adsorption efficiency due to the purine content of the adsorbent itself. Steam explosion opens the dense structure of the wheat residue, exposing purine precursors. The combined enzymes directly degrade nucleic acids, reducing purine sources. Gradient washing further removes residual purines and small molecule impurities, preventing odor generation and ensuring the adsorption effect of the modified wheat residue.

[0027] Optionally, the adsorbent further includes acidified montmorillonite, and the mass ratio of the modified wheat lees to the acidified montmorillonite is (6-8):1.

[0028] Optionally, the preparation method of the acidified montmorillonite includes the following steps:

[0029] Montmorillonite is added to 0.2-0.4 mol / L dilute sulfuric acid, heated to 65-75℃ for 2-4 hours, cooled, centrifuged, washed until neutral, dried, and ground to obtain the final product.

[0030] By adopting the above technical solution, acidified montmorillonite is introduced into the modified wheat lees. The layered structure of acidified montmorillonite increases the specific surface area of ​​the adsorbent, resulting in a larger area for physical adsorption. Under acid treatment conditions, interlayer ions undergo plasma exchange and dissolution, the interlayer lattice cracks, and the interlayer spacing is further expanded.

[0031] Furthermore, the interlayer of montmorillonite exhibits a negative charge, while purines protonate and become positively charged under the weakly acidic conditions of beer. Under the action of electrostatic adsorption, on the one hand, it can significantly enhance the approach of purine substances to the adsorbent and coordinate with the zinc ions of the modified wheat lees; on the other hand, montmorillonite also electrostatically adsorbs purines, further enhancing the adsorbent's removal of purines.

[0032] Secondly, this application provides a low-purine beer, which is prepared by a method for preparing a low-purine beer according to this application.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. This application uses malt residue, a byproduct of beer brewing, as a carrier for further modification and treatment as an adsorbent. It is homologous to the beer fermentation liquid, which effectively prevents the non-specific adsorption and destruction of foam-related proteins and beer flavor substances in beer by the adsorbent. The raw materials are environmentally friendly, inexpensive and readily available, and highly safe. This not only realizes the resource utilization of waste and greatly reduces costs, but also maintains the excellent foam stability and unique taste and flavor of beer itself.

[0035] 2. This application employs steam explosion and gradient water washing processes to depurify the malt grains themselves, and then introduces carboxylic acid groups and zinc ions for chelation, thereby achieving specific capture of purine substances without adsorbing foam proteins and flavor molecules that are key to beer foam performance, thus ensuring the depurification effect of the adsorbent.

[0036] 3. This application further uses a mixture of acidified montmorillonite and modified wheat lees as an adsorbent. Under the interlayer negative charge of acidified montmorillonite, the approach of purine to the adsorbent is accelerated, and the combination of purine and zinc ions is promoted. At the same time, the electrostatic adsorption of acidified montmorillonite itself further enhances the removal of purine by the adsorbent. Detailed Implementation

[0037] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0038] raw material

[0039] Unless otherwise specified, all raw materials used in the embodiments and comparative examples in this application are commercially available products, specifically:

[0040] The barley malt is Australian malt, with a color grade of 4-6 EBC;

[0041] Wheat sprouts, color 2.5-3.5 EBC;

[0042] The hops used are Qingdao hops, sourced from Weifang Lanqiao Craft Beer Raw Material Co., Ltd.

[0043] The brewer's yeast is English ale yeast, Angel CY115;

[0044] The nuclease, FDG-2253, was selected from Ningxia Xiasheng Industrial Group Co., Ltd.

[0045] Cellulase, selected from Ningxia Xiasheng Industrial Group Co., Ltd., FFG-0672;

[0046] Xylanase, selected from Ningxia Xiasheng Industrial Group Co., Ltd., FDG-2221;

[0047] Pectinase, selected from Ningxia Xiasheng Industrial Group Co., Ltd., FFG-3407;

[0048] Neutral protease, selected from Ningxia Xiasheng Industrial Group Co., Ltd., FFG-0657;

[0049] The polypeptide enzyme, selected from Ningxia Xiasheng Industrial Group Co., Ltd., is FDG-2251.

[0050] Montmorillonite is a calcium-based montmorillonite with an interlayer spacing of 1.2-1.5 nm and a specific surface area of ​​240 g / m². 2 .

[0051] Example

[0052] Example 1

[0053] A low-purine beer, the preparation method of which includes the following steps:

[0054] S1: By weight, 18 kg of barley malt and 6 kg of wheat malt are ground and sieved to obtain malt powder, which is then mixed with 3.5 kg of corn flour and 1.5 kg of glutinous rice flour to obtain dry material. The dry material is mixed with water at a material-to-liquid ratio of 1:4 and added to a saccharification pot. The saccharification pot is heated to 51°C at a rate of 2°C / min for saccharification and kept at that temperature for 28 min. Then, the temperature is lowered to 42°C, and pectinase, neutral protease and peptidase are added at a mass ratio of 1:1:1. Saccharification is continued for 25 min to obtain saccharified mash. After passing the iodine test, the temperature is raised to 75°C to filter and wash the mash to obtain the first wort and lees.

[0055] S2: Pour the first wort into a boiling pot and boil for 60 minutes. Add 0.8‰ of the first wort by weight of hops 15 minutes before the end of boiling. After boiling, cool the wort, let it swirl and settle for 15 minutes, and then filter to obtain the second wort.

[0056] S3: Add the second wort to the fermentation tank and aerate it at an oxygen flow rate of 10 mL / min. Add brewer's yeast, with a full inoculation density of 8 × 10⁶ yeast cells. 6 The beer was fermented at 12°C for 7 days, then cooled to 2°C and stored for 7 days to obtain the beer fermentation liquid.

[0057] S4: Add an adsorbent to the beer fermentation liquid for adsorption. The amount of adsorbent added to the beer fermentation liquid is 11.6 g / L, and the adsorption time is 55 min. After filtration, centrifugation, sterilization and packaging are performed to obtain low-purine beer.

[0058] In this embodiment, the adsorbent is modified wheat lees, and the preparation method of modified wheat lees includes the following steps:

[0059] (1) After freeze-drying the wheat lees obtained in step S1, the lees powder was pulverized and then steam-exploded at 1.2 MPa for 100 s. The blasted wheat lees powder was added to sodium citrate-citric acid buffer solution with pH 4.8-5 at a material-liquid ratio of 1:10. Then, 3.5% of the mass of the wheat lees powder was added to the compound enzyme and enzymatically hydrolyzed at 53°C for 4 h. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees. The compound enzyme was nuclease, cellulase and xylanase in a mass ratio of 4:2:1. The enzymatically hydrolyzed wheat lees was then added to water at 85°C at a material-liquid ratio of 1:8. After stirring for 30 min, the mixture was centrifuged. Then, the mixture was added to water at 55°C and stirred for 45 min before centrifugation. Finally, the mixture was washed with water at 30°C, filtered, dried and pulverized to obtain pretreated wheat lees.

[0060] (2) The pretreated wheat lees were added to a citric acid solution at a material-to-liquid ratio of 1:10. The citric acid solution contained 35 g / L of citric acid and 7.6 g / L of sodium hypophosphite. After stirring at room temperature for 0.5 h, the temperature was raised to 75 °C for pre-esterification for 1.5 h, and then the temperature was raised to 160 °C for esterification reaction for 3 h. After cooling, the mixture was filtered, washed until neutral, dried, crushed and sieved to obtain acidified wheat lees.

[0061] (3) Add acidified wheat lees to a 0.22 mol / L zinc chloride solution at a material-to-liquid ratio of 1:15, adjust the pH to 5.5±0.5, shake at 50℃ and 150 r / min for 2.5 h, filter, wash and dry to obtain modified wheat lees.

[0062] Example 2

[0063] A low-purine beer, differing from Example 1 in that step S4 specifically involves:

[0064] An adsorbent was added to the beer fermentation liquid for adsorption. The amount of adsorbent added to the beer fermentation liquid was 8g / L, and the adsorption time was 60min. After filtration, centrifugation, sterilization and packaging were performed to obtain low-purine beer.

[0065] In this embodiment, the adsorbent is modified wheat lees, and the preparation method of modified wheat lees includes the following steps:

[0066] (1) After freeze-drying the wheat lees obtained in step S1, the lees powder was pulverized and then steam-exploded at 1.5 MPa for 50 seconds. The blasted wheat lees powder was added to sodium citrate-citric acid buffer solution with pH 4.8-5 at a material-to-liquid ratio of 1:10. Then, 4% of the weight of the wheat lees powder was added to the compound enzyme and enzymatically hydrolyzed at 50°C for 3 hours. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees. The compound enzyme consisted of nuclease, cellulase and xylanase in a mass ratio of 3:1:1. The enzymatically hydrolyzed wheat lees was then added to water at 80°C at a material-to-liquid ratio of 1:8. After stirring for 30 minutes, the mixture was centrifuged. Then, the mixture was added to water at 50°C and stirred for 45 minutes before centrifugation. Finally, the mixture was washed with water at 25°C, filtered, dried and pulverized to obtain pretreated wheat lees.

[0067] (2) The pretreated wheat lees were added to a citric acid solution at a material-to-liquid ratio of 1:10. The citric acid solution contained 20 g / L of citric acid and 5 g / L of sodium hypophosphite. After stirring at room temperature for 0.5 h, the temperature was raised to 70 °C for pre-esterification for 1 h, and then the temperature was raised to 150 °C for esterification reaction for 3 h. After cooling, the mixture was filtered, washed until neutral, dried, crushed and sieved to obtain acidified wheat lees.

[0068] (3) Add acidified wheat lees to 0.1 mol / L zinc chloride solution at a material-to-liquid ratio of 1:15, adjust the pH to 5.5±0.5, shake at 40℃ and 200 r / min for 2 h, filter, wash and dry to obtain modified wheat lees;

[0069] All other steps are the same as in Example 1.

[0070] Example 3

[0071] A low-purine beer, differing from Example 1 in that step S4 specifically involves:

[0072] An adsorbent is added to the beer fermentation liquid for adsorption. The amount of adsorbent added to the beer fermentation liquid is 15g / L, and the adsorption time is 50min. After filtration, centrifugation, sterilization and packaging are performed to obtain low-purine beer.

[0073] In this embodiment, the adsorbent is modified wheat lees, and the preparation method of modified wheat lees includes the following steps:

[0074] (1) After freeze-drying the wheat lees obtained in step S1, the lees powder was obtained and then steam-exploded under 1 MPa for 150 s. The exploding wheat lees powder was added to sodium citrate-citric acid buffer solution with pH 4.8-5 at a material-liquid ratio of 1:10. Then, 3% of the mass of the wheat lees powder was added to the compound enzyme and enzymatically hydrolyzed at 55℃ for 5 h. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees. The compound enzyme was nuclease, cellulase and xylanase in a mass ratio of 3:2:1. The enzymatically hydrolyzed wheat lees was then added to water at 90℃ at a material-liquid ratio of 1:8. After stirring for 30 min, the mixture was centrifuged. Then, the mixture was added to water at 60℃ and stirred for 45 min before centrifugation. Finally, the mixture was washed with water at 30℃, filtered, dried and pulverized to obtain pretreated wheat lees.

[0075] (2) The pretreated wheat lees were added to a citric acid solution at a material-to-liquid ratio of 1:10. The citric acid solution contained 50 g / L of citric acid and 10 g / L of sodium hypophosphite. After stirring at room temperature for 0.5 h, the temperature was raised to 80 °C for pre-esterification for 2 h, and then the temperature was raised to 160 °C for esterification reaction for 2 h. After cooling, the mixture was filtered, washed until neutral, dried, crushed and sieved to obtain acidified wheat lees.

[0076] (3) Add acidified wheat lees to 0.3 mol / L zinc chloride solution at a material-to-liquid ratio of 1:15, adjust the pH to 5.5±0.5, shake at 60℃ and 150 r / min for 3 h, filter, wash and dry to obtain modified wheat lees;

[0077] All other steps are the same as in Example 1.

[0078] Example 4

[0079] A low-purine beer, differing from Example 1 in that the preparation method of modified malt lees in step S4 does not involve steam explosion of the malt lees powder in step (1). The specific steps of step (1) are as follows:

[0080] After freeze-drying the wheat lees obtained in step S1, the wheat lees powder was added to a sodium citrate-citric acid buffer solution with a pH of 4.8-5 at a material-to-liquid ratio of 1:10. Then, 3.5% of the mass of the wheat lees powder was added to a compound enzyme, and the mixture was enzymatically hydrolyzed at 53°C for 4 hours. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees. The compound enzyme consisted of nuclease, cellulase, and xylanase in a mass ratio of 4:2:1. The enzymatically hydrolyzed wheat lees was then added to water at 85°C at a material-to-liquid ratio of 1:8, stirred for 30 minutes, and centrifuged. The mixture was then added to water at 55°C, stirred for 45 minutes, and centrifuged again. Finally, the mixture was washed with water at 30°C, filtered, dried, and then pulverized to obtain pretreated wheat lees.

[0081] All other steps are the same as in Example 1.

[0082] Example 5

[0083] A low-purine beer, differing from Example 1 in that step (1) of the preparation method of modified malt in step S4 does not use gradient washing to wash the enzymatically hydrolyzed malt. The specific steps of step (1) are as follows:

[0084] After freeze-drying and pulverizing the wheat lees obtained in step S1 to obtain wheat lees powder, steam explosion was carried out under 1.2 MPa for 100 s. The exploded wheat lees powder was added to sodium citrate-citric acid buffer solution with pH 4.8-5 at a material-to-liquid ratio of 1:10. Then, 3.5% of the mass of the wheat lees powder was added to the compound enzyme, and enzymatic hydrolysis was carried out at 53℃ for 4 h. After enzyme inactivation, the mixture was filtered to obtain enzymatically hydrolyzed wheat lees. The compound enzyme consisted of nuclease, cellulase and xylanase in a mass ratio of 4:2:1. The mixture was then washed with water at 55℃, filtered, dried and pulverized to obtain pretreated wheat lees.

[0085] All other steps are the same as in Example 1.

[0086] Example 6

[0087] A low-purine beer, differing from Example 1 in that the preparation method of the modified malt grains in step S4 specifically includes the following steps:

[0088] (1) The wheat lees obtained in step S1 were freeze-dried and then pulverized to obtain wheat lees powder. The powder was added to a citric acid solution at a material-to-liquid ratio of 1:10. The citric acid solution contained 35 g / L of citric acid and 7.6 g / L of sodium hypophosphite. After stirring at room temperature for 0.5 h, the temperature was raised to 75 °C for pre-esterification for 1.5 h, and then the temperature was raised to 160 °C for esterification reaction for 3 h. After cooling, the mixture was filtered, washed until neutral, dried, pulverized and sieved to obtain acidified wheat lees.

[0089] (3) Add acidified wheat lees to a 0.22 mol / L zinc chloride solution at a material-to-liquid ratio of 1:15, adjust the pH to 5.5±0.5, shake at 50℃ and 150 r / min for 2.5 h, filter, wash and dry to obtain modified wheat lees;

[0090] All other steps are the same as in Example 1.

[0091] Example 7

[0092] A low-purine beer, which differs from Example 1 in that the adsorbent in step S4 of this example also includes acidified montmorillonite. The mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent is 6:1. The preparation method of acidified montmorillonite includes the following steps: adding montmorillonite to 0.2 mol / L dilute sulfuric acid, heating to 65°C and reacting for 4 hours, cooling, centrifuging, washing to neutrality, drying, and grinding to obtain acidified montmorillonite;

[0093] All other steps are the same as in Example 1.

[0094] Example 8

[0095] A low-purine beer, differing from Example 1 in that the adsorbent in step S4 of this example further includes acidified montmorillonite, and the mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent is 6:1. The preparation method of acidified montmorillonite includes the following steps: adding montmorillonite to 0.3 mol / L dilute sulfuric acid, heating to 70°C and reacting for 3 hours, cooling, centrifuging, washing to neutrality, drying, and grinding to obtain acidified montmorillonite;

[0096] All other steps are the same as in Example 1.

[0097] Example 9

[0098] A low-purine beer, which differs from Example 1 in that the adsorbent in step S4 of this example also includes acidified montmorillonite. The mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent is 6:1. The preparation method of acidified montmorillonite includes the following steps: adding montmorillonite to 0.4 mol / L dilute sulfuric acid, heating to 75°C and reacting for 2 hours, cooling, centrifuging, washing to neutrality, drying, and grinding to obtain acidified montmorillonite;

[0099] All other steps are the same as in Example 1.

[0100] Example 10

[0101] A low-purine beer, which differs from Example 7 in that the mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent of this example is 7:1, while all other steps are the same as in Example 7.

[0102] Example 11

[0103] A low-purine beer, which differs from Example 7 in that the mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent of this example is 8:1, while the other steps are the same as in Example 7.

[0104] Example 12

[0105] A low-purine beer, which differs from Example 7 in that the mass ratio of modified wheat lees to acidified montmorillonite in the adsorbent of this example is 4:1, while the other steps are the same as in Example 7.

[0106] Comparative Example

[0107] Comparative Example 1

[0108] A low-purine beer, differing from Example 1, in that the preparation method of modified lees in step S4 specifically includes the following steps: the lees obtained in step S1 are freeze-dried and then pulverized to obtain lees powder, which is then subjected to steam explosion at 1.2 MPa for 100 s. The exploded lees powder is added to sodium citrate-citric acid buffer solution with a pH of 4.8-5 at a material-to-liquid ratio of 1:10. Then, 3.5% of the mass of the lees powder of the compound enzyme is added, and enzymatic hydrolysis is performed at 53°C for 4 h. After enzyme inactivation, the mixture is filtered to obtain enzymatically hydrolyzed lees. The compound enzyme is nuclease, cellulase and xylanase in a mass ratio of 4:2:1. The enzymatically hydrolyzed lees is then added to water at 85°C at a material-to-liquid ratio of 1:8, stirred for 30 min and centrifuged. Then, it is added to water at 55°C, stirred for 45 min and centrifuged again. Finally, it is washed with water at 30°C, filtered, dried and pulverized to obtain the final product.

[0109] All other steps are the same as in Example 1.

[0110] Comparative Example 2

[0111] A low-purine beer differs from Example 1 in that the adsorbent in step S4 is unmodified wheat lees, and only the wheat lees powder obtained by freeze-drying and pulverizing the wheat lees obtained in step S1 is used as the adsorbent. All other steps are the same as in Example 1.

[0112] Comparative Example 3

[0113] A low-purine beer, which differs from Example 7 in that the adsorbent is only acidified montmorillonite, while all other steps are the same as in Example 7.

[0114] Comparative Example 4

[0115] A beer, differing from Example 1 in that no adsorbent was added, is prepared using the following method:

[0116] S1: By weight, 18 kg of barley malt and 6 kg of wheat malt are ground and sieved to obtain malt powder, which is then mixed with 3.5 kg of corn flour and 1.5 kg of glutinous rice flour to obtain dry material. The dry material is mixed with water at a material-to-liquid ratio of 1:4 and added to a saccharification pot. The saccharification pot is heated to 51°C at a rate of 2°C / min for saccharification and kept at this temperature for 28 min. Then, the temperature is lowered to 42°C, and pectinase, neutral protease and peptidase are added at a mass ratio of 1:1:1. Saccharification is continued for 25 min to obtain saccharified mash. After passing the iodine test, the temperature is raised to 75°C to filter and wash the mash to obtain the first wort and lees.

[0117] S2: Pour the first wort into a boiling pot and boil for 60 minutes. Add 0.8‰ of the first wort by weight of hops 15 minutes before the end of boiling. After boiling, cool the wort, let it swirl and settle for 15 minutes, and then filter to obtain the second wort.

[0118] S3: Add the second wort to the fermentation tank and aerate it at an oxygen flow rate of 10 mL / min. Add brewer's yeast, with a full inoculation density of 8 × 10⁶ yeast cells. 6 The beer is fermented at 12℃ for 7 days, then cooled to 2℃ and stored for 7 days to obtain the beer fermentation liquid. After filtration, centrifugation, sterilization and packaging are then carried out.

[0119] Performance testing

[0120] The low-purine beers obtained by the preparation methods of Examples 1-12 and Comparative Examples 1-4 were subjected to the following relevant performance tests, and the test results are recorded in Tables 1-2.

[0121] Test Example 1

[0122] Comparative Example 4 represents the beer group that did not use adsorbent treatment. The purine content in the low-purine beers obtained by the preparation methods of Examples 1-12 and Comparative Examples 1-4 was determined by HPLC, and the adsorption removal rate was calculated. The results are recorded in Table 1. Purine adsorption removal rate = (Total purine content of Comparative Example 4 - Total purine content of Examples 1-12) / Total purine content of Comparative Example 4. Chromatographic conditions were as follows:

[0123] (1) Chromatograph: Agilent 1260; Column: C18 column;

[0124] The mobile phase consisted of 997 mL of ultrapure water, 1.5 mL of glacial acetic acid, and 1.5 mL of tetrabutylammonium hydroxide. The organic phase was methanol, with a mobile phase to organic phase volume ratio of 9:1. Isocratic elution was performed. The UV detection wavelength was 254 nm, the flow rate was 1 mL / min, the column temperature was 30 °C, and the injection volume was 10 μL.

[0125] (2) Preparation of standard samples: Take 25 mg each of adenine, guanine, xanthine and hypoxanthine, add 25 mL of ultrapure water to dissolve, add an appropriate amount of 2 mol / L sodium hydroxide to aid dissolution, and obtain a standard stock solution with a standard concentration of 500 mg / L.

[0126] (3) Determination of free purines in beer: Take 20 mL of beer, degas it by sonication for 20 min, filter it through a 0.22 μm filter membrane, and perform chromatographic analysis on the filtrate;

[0127] (4) Determination of total purines in beer samples: Take 10 mL of beer samples from each group, degas them by sonication for 20 min, place them in a 25 mL stoppered test tube, add 10 mL of formic acid and trifluoroacetic acid in a volume ratio of 1:1, immediately place them in a boiling water bath, hydrolyze them at 100 °C for 1 h, filter them quickly in an ice bath, adjust the pH to neutral using KOH solution, filter them using qualitative filter paper, centrifuge the filtrate at 3000 r / min for 10 min, adjust the pH to 4 with dilute phosphoric acid, then add ultrapure water to make up to 50 mL, finally filter them through a 0.22 filter membrane, and perform chromatographic analysis on the filtrate.

[0128] Table 1

[0129] Group Total purine content / mg / L Adsorption removal rate / % Example 1 11.0 85.6 Example 2 12.1 84.2 Example 3 11.6 84.9 Example 4 15.7 79.5 Example 5 14.5 81.1 Example 6 38.1 50.2 Example 7 9.9 87.1 Example 8 10.1 86.8 Example 9 9.6 87.5 Example 10 8.7 88.6 Example 11 8.3 89.2 Example 12 11.8 84.6 Comparative Example 1 49.6 35.2 Comparative Example 2 60.6 20.9 Comparative Example 3 24.5 68.0 Comparative Example 4 76.6 -

[0130] According to the purine content detection results of the beer samples in Examples 1-3 and Comparative Examples 1-2 in Table 1, it can be seen that this application uses lees, a by-product generated during the beer brewing process, as a carrier. Through a modification method of introducing carboxylic acid groups and zinc ions for chelation after purine depurification pretreatment, specific capture of purine substances is achieved, significantly reducing the purine content in the finished beer. Comparative Example 4 is the group that did not use the adsorbent of this application. It can be seen that before and after use, the purine content in the beer was reduced by 84.2-85.6%, and the total purine content in the beer was <12mg / L, showing a significant purine depurification effect.

[0131] In Example 6, no pretreatment for depurination was performed on the lees. As can be seen, the depurination effect dropped sharply. This is because the lees, a byproduct of saccharification filtration, still contains a large amount of purines. Direct use of this product would severely hinder the coordination of metal ions with purines in the beer fermentation liquid, resulting in poor adsorption.

[0132] In Example 4, no steam explosion was used in the depurination pretreatment process, and in Example 5, no gradient washing of wheat lees with water at different temperatures was used. It can be seen that the depurination effect decreased. This is because steam explosion can open up the dense structure of wheat lees, expose purine precursors, and increase the specific surface area of ​​wheat lees. Then, the nucleic acid is directly degraded by the action of the complex enzyme to reduce the source of purine in wheat lees. The gradient water washing method further dissolves and removes residual purines and small molecule impurities, so that the purines in wheat lees can be removed more thoroughly to prevent affecting the adsorption effect of modified wheat lees.

[0133] According to the performance test results of Examples 1 and 7-11, the introduction of acidified montmorillonite into the adsorbent further enhances the adsorbent's removal effect on purines, increasing the adsorption removal rate to 86.8-89.2%.

[0134] A small amount of acidified montmorillonite can significantly enhance the attraction of purine substances to the adsorbent through electrostatic adsorption, thereby achieving the effect of coordination and removal of purine substances with zinc ions in the modified wheat lees. In Example 12, the mass ratio of acidified montmorillonite to modified wheat lees reached 4:1. It can be seen that excessive acidified montmorillonite will weaken the adsorption and removal effect of the adsorbent.

[0135] Comparative Example 3 used only acidified montmorillonite as an adsorbent, indicating that the purine removal effect of acidified montmorillonite alone is not as good as the synergistic effect of acidified montmorillonite and modified wheat lees.

[0136] Test Example 2

[0137] Sensory evaluation: The sensory evaluation team consisted of 10 sensory evaluation members (aged 20-55, 5 males and 5 females). The evaluators had no obvious likes or dislikes for beer. The team members evaluated the appearance, aroma, foam and taste attributes of the beer sample served in a transparent glass three times. The average value was taken as the final sensory evaluation score for each group. The specific evaluation criteria are shown in Table 2, and the sensory evaluation results are shown in Table 3.

[0138] Table 2

[0139]

[0140]

[0141] Table 3

[0142]

[0143] According to the sensory test results of Examples 1-12 and Comparative Examples 1-4 in Tables 2-3, this application uses malt by-products generated during beer brewing as a carrier. Through a modification method of introducing carboxylic acid groups and zinc ions for chelation after purine depurification pretreatment, specific capture of purine substances is achieved without significantly affecting foam proteins and flavor molecules in beer. This significantly reduces the purine content in the finished beer while ensuring the foam performance and unique taste and flavor of the beer.

[0144] The performance test results of Example 1 and Comparative Example 3 show that while acidified montmorillonite can remove purines from beer to some extent, its effect on maintaining beer foam performance and flavor is not as good as that of using modified maltose alone or in combination with modified maltose. The performance test results of Examples 1 and Examples 7-11 show that a small amount of acidified montmorillonite does not significantly affect beer foam performance and flavor. However, in Example 12, an excessive amount of acidified montmorillonite was used, and the beer foam performance and flavor began to decline significantly.

[0145] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing low-purine beer, characterized in that, Includes the following steps: S1: After crushing the malt and sieving it, add water and mix evenly, then heat it to saccharify. After filtering and washing the malt, the first wort and malt residue are obtained. S2: Boil the first wort, add hops before the boiling is finished, cool, swirl to settle, and then filter to obtain the second wort; S3: Add brewer's yeast to the second wort and ferment to obtain beer fermentation liquid; S4: Add an adsorbent to the beer fermentation liquid for adsorption, filter, centrifuge, and sterilize to obtain the product. The adsorbent includes modified wheat lees. The method for preparing the modified wheat lees is as follows: After freeze-drying the wheat lees from step S1, the lees are pulverized to obtain wheat lees powder. The wheat lees powder is then steam-exploded and added to sodium citrate-citric acid buffer solution. 3-4% of the weight of the wheat lees powder is added to a compound enzyme for enzymatic hydrolysis. After enzyme inactivation, the mixture is filtered to obtain enzymatically hydrolyzed wheat lees. The enzymatically hydrolyzed wheat lees are added to water at 75-85℃, stirred, and centrifuged. Then, they are added to water at 50-60℃, stirred, and centrifuged again. Finally, the mixture is washed with water at 25-30℃, filtered, dried, and pulverized to obtain pretreated wheat lees. The pretreated wheat lees are added to a citric acid solution containing 20-50 g / L of citric acid and 5-10 g / L of esterification catalyst. The esterification reaction is carried out at 150-160°C. After cooling, the mixture is filtered, washed until neutral, dried, and pulverized to obtain acidified wheat lees. Add acidified wheat lees to a 0.1-0.3 mol / L zinc salt solution, adjust the pH to 5.5±0.5, shake at 40-60℃ for 2-3 hours, filter, wash and dry to obtain modified wheat lees.

2. The method for preparing low-purine beer according to claim 1, characterized in that, The adsorbent is added to the beer fermentation broth at a rate of 8-15 g / L, and the adsorption time is 50-60 min.

3. The method for preparing low-purine beer according to claim 1, characterized in that, The zinc salt is selected from either zinc chloride or zinc sulfate.

4. The method for preparing low-purine beer according to claim 1, characterized in that, The complex enzyme comprises nuclease, cellulase, and xylanase in a mass ratio of (3-4):(1-2):

1.

5. The method for preparing low-purine beer according to claim 1, characterized in that, The adsorbent also includes acidified montmorillonite, and the mass ratio of the modified wheat lees to the acidified montmorillonite is (6-8):

1.

6. The method for preparing low-purine beer according to claim 5, characterized in that, The preparation method of the acidified montmorillonite includes the following steps: Montmorillonite is added to 0.2-0.4 mol / L dilute sulfuric acid, heated to 65-75℃ for 2-4 hours, cooled, centrifuged, washed until neutral, dried, and ground to obtain the final product.

7. A low-purine beer, characterized in that, It is prepared by the method for preparing a low-purine beer according to any one of claims 1-6.

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