Production method of lime-flavored fruit beer

Abstract

The invention provides a production method of lime-flavored fruit beer, the lime-flavored fruit beer comprises the following raw materials: double-enzyme synergistically-saccharified wort, a composite lime extract, a modified prebiotic compound and the like, the utilization rate of composite malt is increased through double-enzyme saccharification, lime peel and seeds realize full-resource utilization, the activity of prebiotics is guaranteed through modification, and yeast is an acid-resistant mutagenic strain. The preparation method comprises the steps of customized saccharification, composite lime component preparation, gradient variable-pressure fermentation, composite clarification and sterilization and the like, and flavor generation is optimized through precise temperature and pressure control. According to the product disclosed by the invention, the aroma of lime and the aroma of malt are coordinated, the retention rate of vitamin C exceeds 85%, the activity loss rate of prebiotics is less than or equal to 10%, and the product can be stably stored for 12 months at 3 DEG C and has excellent flavor and health value.

Description

Technical Field

[0001] This invention relates to the field of beer manufacturing technology, and in particular to a method for producing lime-flavored fruit beer. Background Technology

[0002] With consumers becoming more health-conscious and pursuing greater diversity in beverage flavors, fruit-flavored beer, combining the rich taste of beer with the refreshing flavor of fruit, has become an important development direction in the beer industry. Among these, lime, a fruit rich in Vitamin C, citric acid, and unique aroma components, is widely used in fruit beer production; however, its application still faces numerous technical bottlenecks.

[0003] Current lime beer brewing technologies suffer from a relatively simple raw material system, often using a single malt to prepare the wort, resulting in a thin flavor profile and a lack of functional components. Lime utilization is limited to juicing the pulp, with essential oils in the peel easily volatilizing and being lost, while lime seeds are mostly treated as waste, leading to low resource utilization. Prebiotics are often added through direct mixing, which is easily decomposed and destroyed during high-temperature saccharification and fermentation, making it difficult to guarantee their functionality. Fermentation yeasts are mostly conventional strains, with low survival rates in the acidic environment provided by lime, resulting in unstable fermentation efficiency and insufficient flavor compound formation. Furthermore, traditional high-temperature sterilization methods easily destroy the active ingredients and flavor compounds in the beer, while single clarification technologies are insufficient for long-term stable clarification, leading to sedimentation problems.

[0004] Furthermore, existing lime-flavored beers generally suffer from poor flavor harmony, short-lived freshness, and difficulty in balancing functionality and taste. For example, some products add artificial acidulants to increase acidity, resulting in a harsh taste; some products add prebiotics, but due to the lack of modification, the activity loss rate exceeds 50% within the product's shelf life; and some products suffer from defects such as a disconnect between lime flavor and beer flavor, and a bitter aftertaste due to improper fermentation process control. These problems severely restrict the improvement of lime-flavored beers' quality and market competitiveness. Therefore, developing a production method for lime-flavored beers with high raw material utilization, unique and harmonious flavor, stable functionality, and efficient preparation process has become an urgent technical need to be addressed in this field. Summary of the Invention

[0005] This invention provides a method for producing lime-flavored fruit beer to overcome the deficiencies in the prior art.

[0006] This invention provides a method for producing lime-flavored fruit beer, comprising the following steps:

[0007] S1. Customized saccharification: Barley malt, caramel malt, and highland barley malt are crushed separately until the malt bran integrity is ≥95%. They are mixed in proportion and then buffered with water at pH 5.0-5.2. The material-to-water ratio is 1:5-6 g / mL. Double enzyme synergistic saccharification is carried out. After filtration, clear malt wort is obtained for later use.

[0008] S2. Preparation of compound lime components: Fresh lime peel is frozen and crushed by liquid nitrogen, and then extracted by supercritical CO2 at a pressure of 30-35 MPa, a temperature of 40-45℃, and a CO2 flow rate of 20-25 L / h to extract essential oil. The oil is then mixed with wall material and spray-dried to form microcapsules. Fresh lime juice and lime seed ultrafine powder are prepared and mixed to form a compound lime extract.

[0009] S3. Gradient Pressure Swing Fermentation: Heat the wort to 95-100℃ and boil for 40-50 minutes. Cool to 55-60℃, add flavor regulators, stir to dissolve, and then cool to 38-42℃. Add modified prebiotic complex and compound lime extract, mix well, and cool to 20-22℃. Inoculate with activated acid-resistant top-fermenting yeast and carry out three-stage fermentation: Stage 1: 20-22℃, tank pressure 0.05-0.08MPa, fermentation 36-48h; Stage 2: 15-17℃, tank pressure 0.1-0.12MPa, fermentation 5-7d; Stage 3: 8-10℃, tank pressure 0.12-0.15MPa, post-ripening 8-10d, to obtain the fermentation broth.

[0010] S4. High-efficiency clarification and low-temperature sterilization: Add magnetic chitosan microsphere clarifying agent to the fermentation broth at a dosage of 0.3-0.5 g / L, and let it stand at 12-15℃ for 12-18 h. Separate the clarifying agent by magnetic field adsorption. Sterilize with pulsed electric field and ultra-high pressure: First, treat with pulsed electric field with an electric field strength of 30-40 kV / cm, a pulse width of 2-3 μs, and a treatment time of 500-600 μs. Then, treat with ultra-high pressure at 350-450 MPa, a temperature of 2-4℃, and a time of 8-12 min. Cool to 0-4℃ to obtain lime beer.

[0011] According to the production method of lime-flavored fruit beer provided by the present invention, the lime-flavored fruit beer comprises the following raw material components by weight: 90-110 parts of dual-enzyme synergistic saccharified malt wort, 15-22 parts of compound lime extract, 3-5 parts of modified prebiotic complex, 0.4-0.6 parts of acid-resistant top-fermenting yeast, 0.2-0.3 parts of flavor regulator, and 130-160 parts of deionized water;

[0012] The dual-enzyme synergistic saccharified malt wort is prepared by mixing barley malt, caramel malt, and highland barley malt in a mass ratio of 5:2:(1-1.5), and then saccharifying it with a thermostable α-amylase and β-glucanase. The malt wort concentration is 10-14°P, wherein the amount of thermostable α-amylase added is 0.02-0.04% of the total mass of malt, and the amount of β-glucanase added is 0.01-0.02% of the total mass of malt.

[0013] The compound lime extract is composed of fresh lime juice, lime peel essential oil microcapsules, and lime seed ultrafine powder in a mass ratio of 8:1:(0.8-1.2), wherein the lime peel essential oil microcapsules use gum arabic-maltodextrin as the wall material and the core-to-wall ratio is 1:3-5.

[0014] The modified prebiotic complex is a mixture of inulin and galactooligosaccharides in a mass ratio of 2:(1-1.5) after extrusion puffing-freeze pulverization, wherein the extrusion puffing temperature is 120-130℃ and the screw speed is 150-180r / min;

[0015] The acid-resistant surface fermentation yeast is a mutant strain of Saccharomyces cerevisiae CGMCC No. 2.1808 selected through ultraviolet mutagenesis, with a survival rate of ≥90% under pH 3.0-3.5 conditions.

[0016] According to a method for producing lime-flavored fruit beer provided by the present invention, the fresh lime juice is prepared by: selecting Hainan small limes with a ripeness of 90-95%, peeling the fruit pulp and mixing it with 0.3-0.5% ascorbyl palmitate to extract the juice, filtering it through a 150-200 mesh ceramic membrane, and concentrating it to a sugar content of 10-12 Brix using reverse osmosis technology, with the temperature controlled at 35-40℃ during the concentration process.

[0017] According to the present invention, a method for producing lime-flavored fruit beer is provided, wherein the preparation process of the lime seed ultrafine powder is as follows: the lime seeds are vacuum dried at 60-70℃ until the moisture content is ≤5%, and then coarsely pulverized and ultrafinely pulverized to a particle size of 1000-1200 mesh, and then microwave sterilized for later use. The microwave sterilization power is 300-400W and the time is 2-3 minutes.

[0018] According to the present invention, a method for producing lime-flavored fruit beer is provided, wherein the flavor modifier is composed of potassium citrate, γ-aminobutyric acid and maltitol mixed in a mass ratio of 1:0.5:(2-3), wherein the purity of γ-aminobutyric acid is ≥99%.

[0019] According to the present invention, a method for producing lime-flavored fruit beer is provided, wherein the specific parameters of the dual-enzyme synergistic saccharification are as follows: initial saccharification temperature 50-52℃, holding temperature for 20-25 min; temperature rise to 63-65℃, adding dual enzymes and holding temperature for 70-80 min; temperature rise to 75-78℃, holding temperature for 15-20 min to inactivate enzymes, and filtering to obtain wort.

[0020] According to the method for producing lime-flavored fruit beer provided by the present invention, the yeast activation method in step S3 is as follows: acid-resistant top-fermenting yeast is inoculated into YPD medium containing 2-3% lime juice, and cultured with shaking at 30-32℃ and 180-220 r / min for 18-20 h until the OD600 value of the bacterial solution is 1.6-1.8 and the viable count is ≥10. 8 CFU / mL.

[0021] According to the production method of lime-flavored fruit beer provided by the present invention, the preparation method of magnetic chitosan microsphere clarifying agent in step S4 is as follows: chitosan is dissolved in 2% acetic acid aqueous solution, 10-15% iron oxide nanoparticles are added, ultrasonically dispersed for 20-30 min, 5% sodium hydroxide solution is added dropwise to adjust the pH to 8.0-8.5, solidified for 2-3 h, washed to neutral, freeze-dried, and sieved to obtain microspheres with a particle size of 50-80 μm.

[0022] According to the production method of lime-flavored fruit beer provided by the present invention, in the three-stage fermentation process in step S3, sterile oxygen at a rate of 0.5-1.0 L / min is introduced into the fermentation tank every 24 hours, with each aeration lasting 10-15 minutes, and the tank pressure is maintained stable after the aeration is completed.

[0023] According to the method for producing lime-flavored fruit beer provided by the present invention, after step S4, a flavor lock-in step is further included: supercritical carbon dioxide is introduced into the sterilized fruit beer, the carbon dioxide content is adjusted to 0.55-0.65 g / L, degassing is performed at 0-4℃ and vacuum degree of 0.02-0.03 MPa for 10-15 min, and after sealing, it is aged in an environment of 2-4℃ for 3-5 days.

[0024] This invention provides a method for producing lime-flavored fruit beer. The method combines compound malt with dual-enzyme saccharification, increasing the saccharification rate of the wort by over 15%, enriching the flavor profile of the fruit beer, including caramel and malt aromas, while also increasing nutritional components such as β-glucan. After modification, the prebiotics exhibit an activity loss rate of less than 10% within the shelf life and demonstrate good compatibility with the beer system, without any stratification or sedimentation issues. The acid-resistant mutagenic yeast achieves a survival rate of ≥90% in acidic environments, shortening the fermentation cycle by 15% and promoting the formation of flavor compounds, resulting in a more harmonious blend of lime and beer aromas. A customized saccharification process achieves a starch hydrolysis rate exceeding 95%, and a pH buffer system ensures stable production, significantly improving raw material utilization. Gradient pressure swing fermentation optimizes flavor compound formation through precise temperature and pressure control, reducing higher alcohol content, preventing bitterness in the aftertaste, and enhancing flavor complexity. A magnetic chitosan clarifying agent increases clarification efficiency by 50%, and the compound sterilization technology kills microorganisms while retaining over 85% of active ingredients, extending the product's shelf life to 12 months. The refreshing aroma of lime blends harmoniously with the rich flavor of malt, offering a balanced acidity and a smooth texture. Rich in prebiotics, dietary fiber, and vitamin C, it provides multiple health benefits, including regulating gut microbiota. It is stable for 12 months at 0-4℃ and for 6 months at room temperature (25℃) without any sedimentation or significant flavor change. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown herein can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0029] This application provides a method for producing lime-flavored fruit beer, with the following core raw materials and dosages: 100 kg of saccharified malt wort with dual enzyme synergistic saccharification, 18 kg of compound lime extract, 4 kg of modified prebiotic complex, 0.5 kg of acid-resistant top-fermenting yeast, 0.25 kg of flavor modifier, and 145 kg of deionized water. The specific specifications of each component are as follows:

[0030] Dual-enzyme synergistic saccharification of malt wort: It is made from 50 kg of barley malt, 20 kg of caramel malt, and 12 kg of highland barley malt. The amount of heat-resistant α-amylase added is 0.03% (based on the total mass of malt), the amount of β-glucanase added is 0.015% (based on the total mass of malt), the malt wort concentration is 12°P, and the reducing sugar content is 13 g / 100 mL.

[0031] Compound lime extract: made by mixing fresh lime juice, lime peel essential oil microcapsules, and lime seed ultrafine powder in a mass ratio of 8:1:1. The lime peel essential oil microcapsules have a core-to-wall ratio of 1:4, and the wall material is gum arabic-maltodextrin (mass ratio 1:1). The lime seed ultrafine powder has a particle size of 1100 mesh and a moisture content of 4.2%.

[0032] Modified prebiotic complex: Inulin after extrusion puffing is mixed with galactooligosaccharides at a mass ratio of 2:1.2, the extrusion puffing temperature is 125℃, and the screw speed is 160r / min.

[0033] Acid-resistant surface fermentation yeast: Saccharomyces cerevisiae CGMCC No. 2.1808 mutant strain, with a survival rate of 92% at pH 3.2, and a viable count of 1.2 × 10⁻⁶ after activation. 8 CFU / mL.

[0034] Flavor modifiers: Potassium citrate 0.05 kg, γ-aminobutyric acid (99.2% purity)

[0035] It is a mixture of 0.025 kg of maltitol and 0.175 kg of maltitol.

[0036] Preparation method steps:

[0037] S1. Customized saccharification preparation of wort: Barley malt, caramel malt, and highland barley malt are crushed separately to ensure 96% husk integrity; after mixing in proportion, citric acid-sodium citrate buffer water at pH 5.1 (material-to-water ratio 1:5.5g / mL) is added, and the saccharification program is started: initial temperature 51℃ is maintained for 22 min, temperature is increased to 64℃, dual enzymes are added and maintained for 75 min, and then temperature is increased to 76℃ and maintained for 18 min to inactivate the enzymes; the wort is filtered using a plate and frame filter press to obtain clear wort for later use.

[0038] S2. Preparation of compound lime components: Preparation of lime peel essential oil microcapsules: 5 kg of Hainan small lime peel was selected, crushed by liquid nitrogen freezing, and then put into a supercritical extraction vessel. The pressure was set at 32 MPa, the temperature at 42 ℃, and the CO2 flow rate at 22 L / h. After extraction for 2 hours, 0.18 kg of lime essential oil was obtained. The essential oil was mixed with 0.72 kg of gum arabic-maltodextrin mixture and spray-dried (inlet air temperature 180 ℃, outlet air temperature 80 ℃) to make microcapsules.

[0039] Preparation of fresh lime juice: Select 20 kg of Hainan small limes with a ripeness of 92%, peel them, mix the pulp with 0.08 kg of ascorbyl palmitate and juice them. After filtering through a 180-mesh ceramic membrane, concentrate the juice to a sugar content of 11 Brix at 38℃ by reverse osmosis to obtain 14.4 kg of lime juice.

[0040] Preparation of lime seed ultrafine powder: Collect 2 kg of lime seeds, vacuum dry at 65℃ to a moisture content of 4.2%, coarsely grind to 20 mesh, then ultrafine grind to 1100 mesh, and sterilize by microwave at 350W for 2.5 min to obtain 1.8 kg of ultrafine powder; mix the above three to make 18 kg of compound lime extract.

[0041] S3, Gradient Pressure Swing Fermentation: Add malt wort to a fermentation tank and heat to 98°C and boil for 45 minutes; cool to 58°C and add flavor regulators, stirring for 10 minutes until completely dissolved; continue cooling to 40°C, add modified prebiotic complex and compound lime extract, stirring for 20 minutes to mix evenly; cool to 21°C and inoculate with activated acid-resistant yeast (activation conditions: 31°C, 200r / min shaking culture for 19 hours, OD600 value 1.7).

[0042] The fermentation process was initiated in three stages: the first stage was at 21°C and 0.06 MPa, fermenting for 42 hours; the second stage was at 16°C and 0.11 MPa, fermenting for 6 days; and the third stage was at 9°C and 0.13 MPa, with post-fermentation for 9 days. During the fermentation process, sterile oxygen was introduced at a rate of 0.8 L / min every 24 hours for 12 minutes each time. After aeration, the tank pressure was kept stable to obtain the fermentation broth.

[0043] S4. High-efficiency clarification, low-temperature sterilization and subsequent treatment: Clarification: Add 0.4 g / L of magnetic chitosan microsphere clarifier (particle size 65 μm) to the fermentation broth and let it stand at 14℃ for 15 h; separate the clarifier by electromagnetic adsorption device to obtain the clarified liquid.

[0044] Composite sterilization: First, it is treated with a pulsed electric field (electric field strength 35kV / cm, pulse width 2.5μs, treatment time 550μs), then transferred to an ultra-high pressure device and treated for 10min at 380MPa and 3℃; then cooled to 2℃.

[0045] Flavor locking: Supercritical carbon dioxide is introduced and the content is adjusted to 0.6 g / L; degassing is carried out at 2℃ and 0.025 MPa for 12 min, and then sealed and aged at 3℃ for 4 days to obtain the finished lime fruit beer.

[0046] Product testing results: The lime beer prepared in this example was tested for physicochemical properties, sensory quality, and stability. The results are as follows:

[0047] Physicochemical indicators: alcohol content 4.2% vol, pH 4.0, vitamin C content 58 mg / 100 mL, dietary fiber content 3.8 g / 100 mL, prebiotic activity retention rate 92%, higher alcohol content

[0048] ≤60mg / 100mL.

[0049] Sensory quality: The product is light yellow-green in appearance, clear and transparent without sediment; the aroma is fresh, with a harmonious blend of lime fruit and malt caramel; the taste is moderately sweet and sour, smooth, and has a mellow aftertaste without bitterness. It was rated by a sensory evaluation panel of 10 people and received an average score of 9.2 out of 10.

[0050] Stability: After 12 months of storage at 3℃, there was no sedimentation or layering, and the flavor remained unchanged; after 6 months of storage at 25℃, all indicators met national standards, and there was no deterioration.

[0051] Therefore, this embodiment provides a method for producing lime-flavored fruit beer. The combination of compound malt and dual-enzyme saccharification increases the saccharification rate of the wort by more than 15%, enriching the flavor profile of the fruit beer, including caramel and malt aromas, while also increasing nutritional components such as β-glucan. After modification, the prebiotics exhibit an activity loss rate of less than 10% within the shelf life and demonstrate good compatibility with the beer system, without any stratification or sedimentation issues. The acid-resistant mutagenic yeast achieves a survival rate of ≥90% in acidic environments, shortening the fermentation cycle by 15% and promoting the formation of flavor compounds, resulting in a more harmonious blend of lime and beer aromas. A customized saccharification process achieves a starch hydrolysis rate exceeding 95%, and a pH buffer system ensures stable production, significantly improving raw material utilization. Gradient pressure swing fermentation optimizes flavor compound formation through precise temperature and pressure control, reducing higher alcohol content, preventing bitterness in the aftertaste, and enhancing flavor complexity. Magnetic chitosan clarifying agent improves clarification efficiency by 50%, and the compound sterilization technology kills microorganisms while retaining over 85% of active ingredients, extending the product's shelf life to 12 months. The refreshing aroma of lime blends harmoniously with the rich flavor of malt, offering a balanced acidity and a smooth texture. Rich in prebiotics, dietary fiber, and vitamin C, it provides multiple health benefits, including regulating gut microbiota. It is stable for 12 months at 0-4℃ and for 6 months at room temperature (25℃) without any sedimentation or significant flavor change.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing lime-flavored fruit beer, characterized in that, Includes the following steps: S1. Customized saccharification: Barley malt, caramel malt, and highland barley malt are crushed separately until the malt bran integrity is ≥95%. They are mixed in proportion and then buffered with water at pH 5.0-5.

2. The material-to-water ratio is 1:5-6 g / mL. Double enzyme synergistic saccharification is carried out. After filtration, clear malt wort is obtained for later use. S2. Preparation of compound lime components: Fresh lime peel is frozen and crushed by liquid nitrogen, and then extracted by supercritical CO2 at a pressure of 30-35 MPa, a temperature of 40-45℃, and a CO2 flow rate of 20-25 L / h to extract essential oil. The oil is then mixed with wall material and spray-dried to form microcapsules. Fresh lime juice and lime seed ultrafine powder are prepared and mixed to form a compound lime extract. S3. Gradient Pressure Swing Fermentation: Heat the wort to 95-100℃ and boil for 40-50 minutes. Cool to 55-60℃, add flavor regulators, stir to dissolve, and then cool to 38-42℃. Add modified prebiotic complex and compound lime extract, mix well, and cool to 20-22℃. Inoculate with activated acid-resistant top-fermenting yeast and carry out three-stage fermentation: Stage 1: 20-22℃, tank pressure 0.05-0.08MPa, fermentation 36-48h; Stage 2: 15-17℃, tank pressure 0.1-0.12MPa, fermentation 5-7d; Stage 3: 8-10℃, tank pressure 0.12-0.15MPa, post-ripening 8-10d, to obtain the fermentation broth. S4. High-efficiency clarification and low-temperature sterilization: Add magnetic chitosan microsphere clarifying agent to the fermentation broth at a dosage of 0.3-0.5 g / L, and let it stand at 12-15℃ for 12-18 h. Separate the clarifying agent by magnetic field adsorption. Sterilize with pulsed electric field and ultra-high pressure: First, treat with pulsed electric field with an electric field strength of 30-40 kV / cm, a pulse width of 2-3 μs, and a treatment time of 500-600 μs. Then, treat with ultra-high pressure at 350-450 MPa, a temperature of 2-4℃, and a time of 8-12 min. Cool to 0-4℃ to obtain lime beer.

2. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, This lime beer, by weight, includes the following raw material components: 90-110 parts of saccharified wort with dual enzyme synergistic saccharification, 15-22 parts of compound lime extract, 3-5 parts of modified prebiotic complex, 0.4-0.6 parts of acid-resistant top-fermenting yeast, 0.2-0.3 parts of flavor modifier, and 130-160 parts of deionized water. The dual-enzyme synergistic saccharified malt wort is prepared by mixing barley malt, caramel malt, and highland barley malt in a mass ratio of 5:2:(1-1.5), and then saccharifying it with a thermostable α-amylase and β-glucanase. The malt wort concentration is 10-14°P, wherein the amount of thermostable α-amylase added is 0.02-0.04% of the total mass of malt, and the amount of β-glucanase added is 0.01-0.02% of the total mass of malt. The compound lime extract is composed of fresh lime juice, lime peel essential oil microcapsules, and lime seed ultrafine powder in a mass ratio of 8:1:(0.8-1.2), wherein the lime peel essential oil microcapsules use gum arabic-maltodextrin as the wall material and the core-to-wall ratio is 1:3-5. The modified prebiotic complex is a mixture of inulin and galactooligosaccharides in a mass ratio of 2:(1-1.5) after extrusion puffing-freeze pulverization, wherein the extrusion puffing temperature is 120-130℃ and the screw speed is 150-180r / min; The acid-resistant surface fermentation yeast is a mutant strain of Saccharomyces cerevisiae CGMCC No. 2.1808 selected through ultraviolet mutagenesis, with a survival rate of ≥90% under pH 3.0-3.5 conditions.

3. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The preparation method of the fresh lime juice is as follows: Select Hainan small limes with a ripeness of 90-95%, peel them, mix the pulp with 0.3-0.5% ascorbyl palmitate and juice them, filter them through a 150-200 mesh ceramic membrane, and concentrate them to a sugar content of 10-12 Brix using reverse osmosis technology. The temperature during the concentration process is controlled at 35-40℃.

4. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The preparation process of the lime seed ultrafine powder is as follows: lime seeds are vacuum dried at 60-70℃ until the moisture content is ≤5%, then coarsely pulverized and ultrafinely pulverized to a particle size of 1000-1200 mesh, and then microwave sterilized for later use. The microwave sterilization power is 300-400W and the time is 2-3min.

5. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The flavor modifier is composed of potassium citrate, γ-aminobutyric acid, and maltitol in a mass ratio of 1:0.5:(2-3), wherein the purity of γ-aminobutyric acid is ≥99%.

6. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The specific parameters for the dual-enzyme synergistic saccharification are as follows: initial saccharification temperature 50-52℃, hold for 20-25 min; heat to 63-65℃, add dual enzymes and hold for 70-80 min; heat to 75-78℃ again, hold for 15-20 min to inactivate the enzymes, and filter to obtain wort.

7. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The yeast activation method in step S3 is as follows: Acid-tolerant surface-fermenting yeast is inoculated into YPD medium containing 2-3% lime juice and cultured with shaking at 30-32℃ and 180-220 r / min for 18-20 h until the OD600 value of the bacterial culture is 1.6-1.8 and the viable count is ≥10⁻⁶. 8 CFU / mL.

8. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, The preparation method of the magnetic chitosan microsphere clarifying agent in step S4 is as follows: Chitosan is dissolved in a 2% acetic acid aqueous solution, 10-15% iron oxide nanoparticles are added, ultrasonically dispersed for 20-30 min, 5% sodium hydroxide solution is added dropwise to adjust the pH to 8.0-8.5, solidified for 2-3 h, washed until neutral, freeze-dried, and sieved to obtain microspheres with a particle size of 50-80 μm.

9. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, In step S3, during the three-stage fermentation process, 0.5-1.0 L / min of sterile oxygen is introduced into the fermenter every 24 hours, with each aeration lasting 10-15 minutes. After the aeration is completed, the pressure in the fermenter is kept stable.

10. The method for producing lime-flavored fruit beer according to claim 1, characterized in that, Step S4 is followed by a flavor lock-in step: supercritical carbon dioxide is introduced into the pasteurized fruit beer, the carbon dioxide content is adjusted to 0.55-0.65 g / L, degassing is performed at 0-4℃ and vacuum degree of 0.02-0.03 MPa for 10-15 min, and then sealed and aged in an environment of 2-4℃ for 3-5 days.