Process for preparing beer through fruit fermentation

Abstract

The invention belongs to the technical field of food fermentation processes, and particularly relates to a process for preparing beer through fruit fermentation. According to the process, three fermentation procedures are adopted, in the first stage, Pichia kluyveri is used for primary fermentation, in the second stage, yeast extract is added, growth conditions of zymophyte are optimized, lactobacillus plantarum LB-1 is inoculated for main fermentation, and in the third stage, bouquet yeast powder is added, so that the flavor of mulberries and the fermentation complexity are improved; sterile air is introduced for first-stage aging, micro-oxygen and nitrogen are alternately introduced for second-stage aging, finally carbon dioxide is introduced for impregnation, and the mulberry beer is obtained. According to the process, the mulberry juice treatment stage and the wort treatment stage are improved, saccharifying enzyme is added during wort treatment to improve the saccharifying efficiency, pectinase is adopted during mulberry treatment to improve the juice yield, oxidase is adopted to reduce the content of phenolic acid substances, and a good and stable environment is provided for later fermentation and aging.

Description

Technical Field

[0001] The invention relates to the technical field of fermentation, and in particular to a process for preparing beer by fermenting fruit. Background Art

[0002] As consumers' demand for personalized, distinctive beverages continues to grow, fruit beer, as a novel product, has garnered widespread attention. Its diverse flavors and relatively low alcohol content make it suitable for a variety of occasions and are particularly popular among young and female consumers.

[0003] Beer brewing has a long history, and the mature brewing technology provides a technical framework for the development of fruit beer, on this basis we can explore process adjustments and innovations after adding fruit.

[0004] Chinese patent application publication number CN 116814348A discloses a turbid pear-flavored sour beer and a preparation method thereof. The pear-flavored sour beer is made from ale malt, wheat malt, autumn pear juice, and caramel malt, and is fermented with lactic acid bacteria and the above yeast without adding exogenous saccharifying enzymes. The pear-flavored sour beer has an original wort concentration of 8-10°P, a fermentation degree of 71-76%, an alcohol content of 3.6-4.0%vol, a color of 9-12 EBC, a turbidity of 90-120 EBC, a bitterness value of 7-10 IBU, a pH of ≤3.6, and a total organic acid content of ≥3.0 mL / 100 mL. The beer has a sweet, slightly sour taste, a rich fruity aroma, and a unique flavor. The resulting beer is golden in color, has a higher color, and has a spicy and pear fruit aroma with a caramel malt aroma. The above technology does not add exogenous saccharifying enzymes, and relies only on lactic acid bacteria and yeast fermentation. The saccharification process may be difficult to control accurately, and has higher requirements for fermentation conditions. Slight deviations may affect the stability of indicators such as fermentation degree and alcohol content, increasing the difficulty of production control. Compared with some processes that add auxiliary means such as saccharifying enzymes, the fermentation efficiency may be lower, which will extend the production cycle and reduce production capacity, and is not conducive to large-scale industrial rapid production.

[0005] Chinese patent application publication number CN 118165793 A discloses a process for producing fruit fermented beer. Peach granules and water are mixed, inoculated with a complex bacterial strain, enzymes, bacterial cellulose, and cyanobacteria, and subjected to initial fermentation, squeezing, filtration, and boiling to produce white peach juice. Barley malt is then saccharified and boiled, then inoculated with brewer's yeast and fermented to produce barley beer. The white peach juice is then added to the barley beer and fermented to produce the finished fermented beer. The synergistic effects of the microorganisms and additives used in this process are complex, requiring stringent control of fermentation conditions. Summary of the Invention

[0006] The present invention provides a process for producing beer through fruit fermentation. This process employs co-fermentation of mulberry juice and wort, imparting a unique fruity aroma and color to the beer, enriching its flavor profile and distinguishing it from traditional beers. Enzymes are rationally utilized to improve raw material utilization. Multi-stage fermentation, the use of multiple microorganisms, and ultrasound-assisted co-fermentation facilitate the production of a variety of flavor substances. A sophisticated aging process promotes oxidation reactions while preventing over-oxidation, further enhancing the integration and stabilization of flavor substances and improving the overall quality of the beer.

[0007] The present invention provides a process for preparing beer by fermenting fruit, comprising:

[0008] Step S1: adding water to frozen mulberries, crushing them, adding pectinase, white sugar, and oxidase, stirring, filtering, and sterilizing to obtain mulberry juice;

[0009] Step S2: pulverizing malt, adding saccharifying enzyme, soaking in hot water, heating, and filtering to obtain wort;

[0010] Step S3: mulberry juice and wort are mixed and added to a fermentation tank, and Pichia kluyveri is added to perform the first stage fermentation;

[0011] Step S4: soaking the tea leaves in hot water, filtering to obtain tea juice, cooling the tea juice, adding the tea juice into a fermentation tank, adding yeast extract, inoculating Lactobacillus plantarum LB-1, and performing a second stage fermentation with ultrasound assistance;

[0012] Step S5: adding Brettanomyces powder to carry out the third stage of fermentation, and filtering to obtain the fermentation liquid;

[0013] Step S6: introducing sterile air into the fermentation liquid to perform the first stage of aging;

[0014] Step S7: Cooling, recovering the yeast, transferring it to a stainless steel barrel, alternately introducing micro-oxygen and nitrogen, performing the second stage of aging, adding an antioxidant, and obtaining a mature fermentation broth;

[0015] Step S8: The mature fermentation liquid is impregnated with carbon dioxide, a clarifier is added, and the liquid is filtered, filled, and sterilized to obtain mulberry beer.

[0016] Preferably, in step S1, the oxidase is any one or more of monophenol oxidase, polyphenol oxidase, and laccase, which are used to degrade substances such as tannins and phenolic acids in mulberry juice.

[0017] Preferably, in step S1, the stirring temperature is 30-45° C., and the stirring time is 1-3 h.

[0018] Preferably, in step S1, the sterilization temperature is 90-95° C., and the sterilization time is 3-5 minutes.

[0019] Preferably, in step S1, the mass ratio of the mulberry, water, pectinase, sugar and oxidase is 1: (0.55-0.72): (0.05-0.1): (0.02-0.05): (0.01-0.05).

[0020] Preferably, in step S2, the malt is any one or more of barley malt and wheat malt.

[0021] Preferably, in step S2, the temperature of the hot water is 40-50° C.; and the soaking time is 0.5-1 h.

[0022] Preferably, in step S2, the heating process is to first boil for 1 to 3 minutes, adjust the temperature to 80 to 85° C., maintain for 3 to 5 minutes, and then continue heating to 70 to 75° C., and maintain for 5 to 15 minutes.

[0023] Preferably, in step S2, the mass ratio of the malt, hot water and saccharifying enzyme is 1:(2-3):(0.05-0.1).

[0024] Preferably, in step S3, the temperature of the first stage fermentation is 15-20° C., and the time is 2-3 days.

[0025] Preferably, in step S3, the amount of Pichia kluyveri used is (10-30) g / L.

[0026] Preferably, in step S3, the volume ratio of the mulberry juice to the wort is 1:(0.2-0.5).

[0027] Preferably, in step S4, the tea leaves are any one or more of black tea, green tea, oolong tea, white tea, and dark tea.

[0028] Preferably, in step S4, the temperature of the hot water is 70-90° C., and the mass ratio of the tea leaves to the hot water is 1:(30-60).

[0029] Preferably, in step S4, the soaking time is 0.5 to 1 hour.

[0030] Preferably, in step S4, the amount of tea juice added is (100-200) mL / L.

[0031] Preferably, in step S4, the amount of the yeast extract is (20-40) g / L.

[0032] Preferably, in step S4, the inoculation amount of the Lactobacillus plantarum LB-1 is 1-3%.

[0033] Preferably, in step S4, the parameters of the ultrasonic-assisted fermentation device are set to a frequency of 20 to 30 kHz, a power of 200 to 300 W, a total ultrasonic time of 1 to 2 hours, and a duration of 5 to 15 minutes per ultrasonic cycle.

[0034] Preferably, in step S4, the temperature of the second stage fermentation is 20-25° C., and the fermentation time is 2-3 days.

[0035] Preferably, in step S5, the amount of Brettanomyces powder used is 0.5-2 g / L.

[0036] Preferably, in step S5, the temperature of the third stage fermentation is 18-22° C., and the fermentation time is 1-2 days.

[0037] Preferably, in step S6, the flow rate of the sterile air is 0.2 to 0.5 L / min.

[0038] Preferably, in step S6, the stirring time is 10 to 30 minutes.

[0039] Preferably, in step S6, the temperature of the first stage aging is 15-20° C., and the aging time is 1-2 days.

[0040] Preferably, in step S7, the temperature is lowered to 6-8° C.; and the antioxidant is any one or more of vitamin C, sodium erythorbate, and vitamin E.

[0041] Preferably, in step S7, the amount of antioxidant added is (0.2-0.5) g / L.

[0042] Preferably, in step S7, the flow rate of the micro-oxygen is 0.1 to 0.3 L / min, and the time is 20 to 30 min.

[0043] Preferably, in step S7, the flow rate of nitrogen is 0.1 to 0.2 L / min, and the time is 20 to 30 min.

[0044] Preferably, in step S7, the temperature of the second stage aging is 0-4° C., and the aging time is 2-3 days.

[0045] Preferably, in step S8, the clarifier is any one or more of diatomaceous earth and edible gelatin.

[0046] Preferably, in step S8, the amount of the clarifier is (1-5) g / L.

[0047] Preferably, in step S8, the sterilization temperature is 70-80° C., and the sterilization time is 8-10 minutes.

[0048] Preferably, in step S8, the flow rate of the carbon dioxide is 1-2 L / min, and the pressure in the barrel is 0.1-0.3 Pa.

[0049] Preferably, in step S8, the temperature of the carbon dioxide impregnation is 22-26° C., and the impregnation time is 3-5 days.

[0050] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0051] (1) In order to improve the flavor and level of beer produced by fermenting mulberries, the present application adopts multiple fermentations in different stages, with different fermentation bacteria and processes used in each stage to improve the quality of the beer. In the first stage, Pichia kluyveri is used for primary fermentation, which quickly utilizes the sugar in the mulberries for fermentation to produce aroma substances such as esters, alcohols, and aldehydes, giving the wine a rich fruity aroma. In the second stage, the main fermentation process uses Lactobacillus plantarum LB-1 as the fermentation bacteria, adds yeast extract to promote the reproduction of the fermentation bacteria, uses ultrasound to assist in improving the efficiency of fermentation, and adds tea to enrich the taste and level, producing a unique flavor while inhibiting the reproduction of harmful microorganisms. In the third stage, Brettanomyces is used for the final fermentation to promote the fusion of the natural aroma in the mulberries and the aroma of the tea, making the fruit wine richer in taste and flavor.

[0052] (2) The preparation process of the present application also adopts multiple aging in stages during the aging stage to improve the aging potential and quality of mulberry beer. In the first stage, sterile air is introduced to reduce diacetyl, reduce the content of undesirable flavor substances, improve the flavor quality of the fruit wine, and promote the maturation of the wine body; in the second stage, antioxidants are added and placed in a stainless steel barrel, alternately filled with micro-oxygen and nitrogen for the second stage of aging, which promotes the stability of pigments and maintains freshness; stainless steel barrels can provide a closed, corrosion-resistant and stable environment, and the aging conditions can be precisely controlled during production. The third stage of aging uses carbon dioxide impregnation to promote the production of more aroma components such as esters and higher alcohols in an anaerobic environment, stabilize the color, and inhibit the growth of microorganisms.

[0053] (3) Different enzymes are used in the preparation process of the present application to treat mulberry juice and wort. When preparing mulberry juice, pectinase is used to degrade the pectin in the mulberry peel, destroy the cell structure, significantly increase the juice yield, and reduce the viscosity of the mulberry juice; saccharifying enzyme is used to improve the efficiency of malt saccharification, increase the wort yield, reduce the viscosity of the wort, facilitate the filtration and clarification of the wort, and improve the transparency and quality of the wort; oxidase is used to promote the degradation of tannins and phenolic acids in mulberry juice, reduce their inhibitory effect on fermentation bacteria, and reduce the risk of oxidative browning, excessive astringency, and cold turbidity during mulberry juice fermentation. The present application uses oxidases such as monophenol oxidase and polyphenol oxidase to catalyze the oxidation of phenols, reduce the content of tannins and phenolic acids in mulberry juice, and provide a good and stable environment for later fermentation and aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A process flow chart for producing beer by fermenting a fruit.

[0055] Figure 2 This is a picture of a mulberry beer. DETAILED DESCRIPTION

[0056] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0057] The Lactobacillus plantarum LB-1 used in the Examples and Comparative Examples was purchased from the China General Microbiological Culture Collection Center, classified and named Lactobacillus plantarum, and has a collection number of CGMCC NO.18215.

[0058] The yeast extract used in the examples and comparative examples was purchased from Chr. Hansen A / S, product model: 11PIGLOB EN 05-28-2024.

[0059] The Pichia kluyveri used in the Examples and Comparative Examples was purchased from Chr. Hansen A / S, product model: 3PI GLOB EN 06-21-2024.

[0060] The Brettanomyces powder used in the Examples and Comparative Examples was purchased from Shanghai Fusheng Industrial Co., Ltd. The strain number is ATCC 20233 and the classification name is Brettanomyces intermedius.

[0061] The liquid culture medium formula used for Lactobacillus plantarum LB-1 is as follows: peptone 10 g / L, beef extract 5 g / L, yeast extract 4 g / L, glucose 20 g / L, dipotassium hydrogen phosphate 2 g / L, sodium acetate 5 g / L, ammonium citrate tribasic 2 g / L, magnesium sulfate 0.2 g / L, manganese sulfate 0.05 g / L, and Tween 80 1.0 mL / L. The volume is made up to 1000 mL with distilled water and sterilized at 121°C for 15 min. The culture medium pH is 6.5.

[0062] The solid culture medium formula used for Lactobacillus plantarum LB-1 is as follows: 15 g / L agar powder is added to the liquid culture medium, sterilized at 121° C. for 15 min, and the culture medium pH is 6.5.

[0063] Steps for culturing Lactobacillus plantarum LB-1 seed solution:

[0064] (1) Take 100 μL of Lactobacillus plantarum LB-1 preserved in glycerol, inoculate it into 10 mL of MRS liquid culture medium, and culture it in a constant temperature incubator at 28°C for 18 h to obtain activated Lactobacillus plantarum LB-1;

[0065] (2) Take the activated Lactobacillus plantarum LB-1, draw three lines on MRS solid medium, and culture at 28°C for 48 hours to obtain a single colony of Lactobacillus plantarum LB-1;

[0066] (3) Pick a single colony of Lactobacillus plantarum LB-1, inoculate it into 10 mL of LMRs liquid culture medium, and culture it at 28°C for 18 h to obtain a Lactobacillus plantarum LB-1 bacterial solution;

[0067] (4) Take 6 mL of Lactobacillus plantarum LB-1 bacterial solution and inoculate it into 200 mL of LMRs liquid culture medium to obtain Lactobacillus plantarum LB-1 seed solution.

[0068] The culture medium used for bacterial index detection is MacConkey agar medium with the following formula: peptone 20 g / L, lactose 10 g / L, ox bile salt 5 g / L, sodium chloride 5 g / L, neutral red 0.075 g / L, agar 10 g / L. The volume was made up to 1000 mL with distilled water and sterilized at 121°C for 15 min. The pH of the culture medium was 7.1±0.2.

[0069] Example 1

[0070] like Figure 1 As shown, a fruit beer, the preparation process of which comprises the following steps:

[0071] Step S1: After 5 kg of mulberries are frozen, 2.75 kg of water is added, the mixture is put into a wall-breaking machine and crushed, 250 g of pectinase, 100 g of white sugar, and 50 g of polyphenol oxidase are added, the mixture is stirred at 30° C. for 3 h, the residue is filtered, and the mixture is sterilized at 90° C. for 5 min to obtain mulberry juice.

[0072] Step S2: 5 kg of barley malt was crushed, 250 g of saccharifying enzyme was added, and the mixture was soaked in 15 kg of 40° C. hot water for 1 hour, boiled for 1 minute, kept at 80° C. for 5 minutes, and kept at 70° C. for 15 minutes. The residue was filtered to obtain wort.

[0073] Step S3: 5 L of mulberry juice was mixed with 1 L of wort, added to a fermentation tank, 60 g of Pichia kluyveri was added, and fermented at 15° C. for 3 days.

[0074] Step S4: soak 100 g of black tea in 5 L of 80° C. hot water for 0.5 h, filter to obtain tea juice, add 600 mL of cooled tea juice to a fermentation tank, add 120 g of yeast extract, add 66 mL of Lactobacillus plantarum LB-1 seed liquid, set the frequency of the ultrasonic-assisted fermentation device to 30 kHz, the power to 200 W, the total generation time to 1 h, each duration to 5 min, start the device, and ferment at 25° C. for 2 d.

[0075] Step S5: adding 3.3 g of Brettanomyces powder, fermenting at 18° C. for 2 days, filtering the residue, and obtaining a fermentation liquid.

[0076] Step S6: Sterile air was introduced into the fermentation liquid at a rate of 0.2 L / min, the mixture was stirred for 10 min, and aged at 15° C. for 2 d.

[0077] Step S7: Cooling to 6°C, recovering the yeast, adding 1.32 g of vitamin C, transferring the mixture to a stainless steel barrel, and introducing micro-oxygen at a flow rate of 0.1 L / min and nitrogen at a flow rate of 0.1 L / min into the barrel for 30 min, alternating between the two processes, and aging the mixture at 0°C for 3 days to obtain a mature fermentation broth.

[0078] Step S8, introducing carbon dioxide into the mature fermentation liquid at a flow rate of 1 L / min, adjusting the pressure in the barrel to 0.3 Pa, soaking for 3 days, adding 7 g of diatomaceous earth, filtering the residue, filling, and sterilizing at 70° C. for 10 minutes to obtain mulberry beer.

[0079] Example 2

[0080] like Figure 1 As shown, a fruit beer, the preparation process of which comprises the following steps:

[0081] Step S1: After 5 kg of mulberries are frozen, 3 kg of water is added, the mixture is put into a wall-breaking machine and crushed, 325 g of pectinase, 150 g of white sugar, and 100 g of monophenol oxidase are added, the mixture is stirred at 35 ° C for 2 h, the residue is filtered, and the mixture is sterilized at 95 ° C for 3 min to obtain mulberry juice.

[0082] Step S2: 5 kg of barley malt was crushed, 350 g of saccharifying enzyme was added, and the mixture was soaked in 10 kg of 45° C. hot water for 0.5 h, boiled for 2 min, kept at 80° C. for 4 min, and kept at 70° C. for 10 min, and the residue was filtered to obtain wort.

[0083] Step S3: 5 L of mulberry juice was mixed with 1.5 L of wort, added to a fermentation tank, 90 g of Pichia kluyveri was added, and fermented at 17° C. for 3 days.

[0084] Step S4: soak 100 g of green tea in 3 L of 90° C. hot water for 0.5 h, filter to obtain tea juice, add 650 mL of cooled tea juice to a fermenter, add 160 g of yeast extract, add 143 mL of Lactobacillus plantarum LB-1 seed liquid, set the frequency of the ultrasonic-assisted fermentation device to 30 kHz, the power to 300 W, the total generation time to 1 h, each duration to 10 min, start the device, and ferment at 20° C. for 3 d.

[0085] Step S5: adding 5.4 g of Brettanomyces powder, fermenting at 20° C. for 2 days, filtering the residue, and obtaining a fermentation liquid.

[0086] Step S6: Sterile air was introduced into the fermentation liquid at a rate of 0.3 L / min, the mixture was stirred for 20 min, and the mixture was aged at 17° C. for 2 d.

[0087] Step S7, cooling to 7°C, recovering the yeast, adding 156 g of o-diphenol oxidase, reacting at 35°C for 1 hour, then transferring to a stainless steel barrel, passing micro-oxygen into the barrel at a flow rate of 0.2 L / min for 30 minutes, and passing nitrogen into the barrel at a flow rate of 0.2 L / min for 20 minutes, alternating between the two, aging at 2°C for 3 days, adding 2.15 g of sodium isoascorbate, and obtaining a mature fermentation broth.

[0088] Step S8, introducing carbon dioxide into the mature fermentation liquid at a flow rate of 2 L / min, adjusting the pressure in the barrel to 0.2 Pa, soaking for 2 days, adding 22 g of edible gelatin, filtering the residue, filling, and sterilizing at 80° C. for 9 minutes to obtain mulberry beer.

[0089] Example 3

[0090] like Figure 1 As shown, a fruit beer, the preparation process of which comprises the following steps:

[0091] Step S1: After freezing 5 kg of mulberries, add 3.5 kg of water, put them into a wall-breaking machine and crush them, add 425 g of pectinase, 200 g of white sugar, and 200 g of laccase, stir at 40 ° C for 1.5 h, filter the residue, and sterilize at 90 ° C for 5 min to obtain mulberry juice.

[0092] Step S2: 5 kg of wheat malt was crushed, 400 g of saccharifying enzyme was added, and the mixture was soaked in 15 kg of 40° C. hot water for 1 hour, boiled for 1 minute, kept at 85° C. for 3 minutes, and kept at 75° C. for 10 minutes, and the residue was filtered to obtain wort.

[0093] Step S3: 5 L of mulberry juice was mixed with 2 L of wort, added to a fermentation tank, 120 g of Pichia kluyveri was added, and fermented at 18° C. for 2 days.

[0094] Step S4: soak 100 g of white tea in 4 L of 85° C. hot water for 1 h, filter to obtain tea juice, add 1400 mL of cooled tea juice to a fermentation tank, add 210 g of yeast extract, add 210 mL of plant lactobacillus LB-1 seed liquid, set the ultrasound-assisted fermentation device frequency to 20 kHz, the power to 200 W, the total generation time to 2 h, each duration to 15 min, start the device, and ferment at 25° C. for 2 d.

[0095] Step S5: adding 8.7 g of Brettanomyces powder, fermenting at 22° C. for 1 day, filtering the residue, and obtaining a fermentation liquid.

[0096] Step S6: Sterile air was introduced into the fermentation liquid at a rate of 0.4 L / min, the mixture was stirred for 25 min, and aged at 18° C. for 1 day.

[0097] Step S7: cooling to 8°C, recovering the yeast, adding 435 g of laccase, reacting at 40°C for 1 h, then transferring to a stainless steel barrel, passing micro-oxygen into the barrel at a flow rate of 0.3 L / min for 20 min, and passing nitrogen into the barrel at a flow rate of 0.1 L / min for 30 min, alternating between the two processes, aging at 3°C ​​for 2 days, adding 3.3 g of vitamin E, and obtaining a mature fermentation broth.

[0098] Step S8, introducing carbon dioxide into the mature fermentation liquid at a flow rate of 1 L / min, adjusting the pressure in the barrel to 0.3 Pa, soaking for 3 days, adding 26 g of diatomaceous earth, filtering the residue, filling, and sterilizing at 70° C. for 10 minutes to obtain mulberry beer.

[0099] Example 4

[0100] like Figure 1 As shown, a fruit beer, the preparation process of which comprises the following steps:

[0101] Step S1: After freezing 5 kg of mulberries, add 3.6 kg of water, put them into a wall-breaking machine and crush them, add 500 g of pectinase, 250 g of white sugar, and 250 g of polyphenol oxidase, stir at 45 ° C for 1 hour, filter the residue, and sterilize at 95 ° C for 3 minutes to obtain mulberry juice.

[0102] Step S2: 5 kg of wheat malt was crushed, 500 g of saccharifying enzyme was added, and the mixture was soaked in 10 kg of 45° C. hot water for 0.5 h, boiled for 1 min, kept at 85° C. for 3 min, and kept at 75° C. for 5 min, and the residue was filtered to obtain wort.

[0103] Step S3: 5 L of mulberry juice was mixed with 2.5 L of wort, added to a fermentation tank, 150 g of Pichia kluyveri was added, and fermented at 20° C. for 2 days.

[0104] Step S4: 100 g of oolong tea was soaked in 6 kg of 75° C. hot water for 1 h, and the tea juice was filtered to obtain tea juice. 1500 mL of the cooled tea juice was added to a fermentation tank, 300 g of yeast extract was added, and 270 mL of Lactobacillus plantarum LB-1 seed liquid was added. The ultrasound-assisted fermentation device was set to a frequency of 20 kHz and a power of 300 W, with a total generation time of 2 h and a duration of 15 min each time. The device was started and fermented at 20° C. for 3 d.

[0105] Step S5: adding 18.6 g of Brettanomyces powder, fermenting at 22° C. for 1 day, filtering the residue, and obtaining a fermentation liquid.

[0106] Step S6: introducing sterile air into the fruit beer fermentation liquid at a rate of 0.5 L / min, stirring for 30 minutes, and aging at 20° C. for 1 day.

[0107] Step S7: cooling to 8°C, recovering the yeast, adding 235 g of monophenol oxidase, and then transferring to a stainless steel barrel. Micro-oxygen was introduced into the barrel at a flow rate of 0.2 L / min for 20 min, and nitrogen was introduced into the barrel at a flow rate of 0.2 L / min for 20 min, alternating between the two processes. The mixture was aged at 4°C for 2 days, and 4.5 g of vitamin E was added to obtain a mature fermentation broth.

[0108] Step S8: introducing carbon dioxide into the mature fermentation broth at a flow rate of 2 L / min, adjusting the pressure in the barrel to 0.3 Pa, soaking for 2 days, adding 45 g of edible gelatin, filtering the residue, filling, and sterilizing at 80° C. for 8 minutes to obtain mulberry beer.

[0109] Comparative Example 1

[0110] A fruit beer, the preparation process of which is different from that of Example 1 in that Pichia kluyveri is not added for fermentation in step S3.

[0111] Comparative Example 2

[0112] A fruit beer, the preparation process of which is different from that of Example 1 in that yeast extract is not added in step S4.

[0113] Comparative Example 3

[0114] A fruit beer, the preparation process of which is different from that of Example 1 in that ultrasound-assisted fermentation is not used in step S4.

[0115] Comparative Example 4

[0116] A fruit beer, the preparation process of which is different from that of Example 1 in that Brettanomyces is not added in step S5.

[0117] Comparative Example 5

[0118] A fruit beer, the preparation process of which is different from that of Example 1 in that micro-oxygen and nitrogen are not alternately introduced in step S7.

[0119] Comparative Example 6

[0120] A fruit beer, the preparation process of which is different from that of Example 1 in that carbon dioxide impregnation is not used in step S8.

[0121] Comparative Example 7

[0122] A fruit beer, the preparation process of which is different from that of Example 1 in that monophenol oxidase is not added in step S1.

[0123] Performance testing:

[0124] 1. Physical and chemical property testing: According to the method specified in GB / T 4927, the apparent sugar content, total acidity and turbidity of the fruit beers prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were tested.

[0125] 2. Bacterial index detection: Detect intestinal pathogens such as Escherichia coli in the fruit beer prepared in Examples 1 to 4 and Comparative Examples 1 to 6. The specific operation is as follows:

[0126] (1) Using a sterile sampling tool, collect appropriate amounts of the fruit beer samples prepared in Examples 1 to 4 and Comparative Examples 1 to 4.

[0127] (2) Dilute the sample with PBS buffer solution to 10 3 times, take 5 μL of the sample and spread it on MacConkey agar medium, culture it at 36±1℃ for 18 h, and count the colonies on the plate.

[0128] 3. Fruity flavor detection: The fruity aroma of the fruit beers prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was scored by 10 testers, all of whom were nationally certified wine tasters.

[0129] Table 1 Physical and chemical properties data

[0130]

[0131] As shown in Table 1, the fruit beers prepared using the processes of Examples 1-4 had moderate sugar content and total acidity. Comparative Example 1 did not utilize Pichia kluyveri for the first stage of fermentation, Comparative Example 2 did not add yeast extract during the second stage of fermentation, and Example 3 did not utilize ultrasound-assisted fermentation. Therefore, compared to Examples 1-4, the sugars in the fruit were not fully fermented, resulting in excessive sugar content and a compromised taste. Comparative Example 4 did not utilize Brettanomyces during the third stage of fermentation, resulting in a higher content of acidic substances in the beer, resulting in a lower sugar content and higher total acidity. The turbidity of the fruit beers prepared in Examples 1-4 and Comparative Examples 1-6 was similar, with relatively clear, free of residue and suspended matter. Comparative Example 7 did not utilize oxidase, resulting in higher levels of tannins and phenolic acids in the mulberry juice, which in turn inhibited later fermentation and aging, resulting in a more astringent beer and increased turbidity during low-temperature aging.

[0132] Table 2 Bacterial index detection data

[0133]

[0134] Note: The number of Escherichia coli in each milliliter of wine shall not exceed 3MPN; the number of Staphylococcus aureus shall not exceed 100CFU / mL; and Salmonella shall not be detected.

[0135] As shown in Table 2, no Salmonella was detected in the fruit beers prepared using the processes of Examples 1 to 4 and Comparative Examples 1 to 7, no Escherichia coli was detected in Example 1, Example 3, Comparative Examples 1 to 5, and Comparative Example 7, and no Staphylococcus aureus was detected in Example 2, Example 4, Comparative Examples 1 to 2, and Comparative Examples 4 to 5. The detection values ​​of the remaining Examples and Comparative Examples were also within the specified range.

[0136] Table 3 Fruity flavor detection and evaluation table

[0137] Sample number Appearance fruity Example 1 Purple-black, clear 10 Example 2 Purple-black, clear 9.85 Example 3 Purple, clear 10 Example 4 Purple, clear 9.63 Comparative Example 1 Deep purple, clear 5.43 Comparative Example 2 Deep purple, clear 5.92 Comparative Example 3 Deep purple, clear 5.86 Comparative Example 4 Purple, clear 7.58 Comparative Example 5 Purple, clear 7.73 Comparative Example 6 Purple, clear 7.67 Comparative Example 7 Brown, with suspended matter 6.56

[0138] Note: A strong fruity aroma is 10 points → no fruity aroma is 0 points.

[0139] As shown in Table 3, in the preparation processes of Examples 1 and 2, the fruit beer prepared using barley malt is purple-black, and in the preparation processes of Examples 3 and 4, the fruit beer prepared using wheat malt is purple-red. The fruit beers prepared in Examples 1 to 4 are all uniform in color and clear; the preparation processes of Comparative Examples 1 to 3 are different from those of Example 1 in the fermentation process, and the colors of the prepared wines are different. The processes of the aging stages of Comparative Examples 4 to 7 are different from those of Example 1, and the colors of the obtained wines are also different from those of Example 1. Combined with the fruit aroma evaluation, the fermentation degree of the wines prepared in Comparative Examples 1 to 3 is lower than that in Example 1, and the colors of the obtained wines are slightly different. The aging methods in the aging stages of Comparative Examples 4 to 6 are different, and the colors are lighter than those in Example 1. In Comparative Example 7, no oxidase is added during the mulberry juice processing stage, resulting in a higher content of tannins and phenolic acids in the mulberry juice, thereby inhibiting fermentation, and producing browning during the fermentation process, with more precipitation during later processing.

[0140] The average fruit aroma evaluation of the fruit beer prepared by the processes of Examples 1 to 4 by ten tasters was above 9 points, indicating a strong fruit aroma; the fruit beer prepared by the processes of Comparative Examples 1 to 3 was evaluated at 5 to 6 points, with a lighter fruit aroma, indicating that there were certain defects in the preparation process; the mulberry beer prepared by the processes of Comparative Examples 4 to 7 was evaluated at 6 to 8 points, with a fruit aroma between that of Examples 1 to 4 and Comparative Examples 1 to 3.

[0141] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing beer by fermenting fruit, characterized in that: The following steps are involved: Step S1: adding water to frozen mulberries, crushing them, adding pectinase, white sugar, and oxidase, stirring, filtering, and sterilizing to obtain mulberry juice; Step S2: pulverizing malt, adding saccharifying enzyme, soaking in hot water, heating, and filtering to obtain wort; Step S3: mulberry juice and wort are mixed and added to a fermentation tank, and Pichia kluyveri is added to perform the first stage fermentation; Step S4: soaking the tea leaves in hot water, filtering to obtain tea juice, cooling the tea juice, adding the tea juice to a fermentation tank, adding yeast extract, inoculating Lactobacillus plantarum LB-1, and performing a second stage fermentation with ultrasound assistance; Step S5: adding Brettanomyces powder to carry out the third stage of fermentation, and filtering to obtain the fermentation liquid; Step S6: introducing sterile air into the fermentation liquid and stirring to perform the first stage of aging; Step S7: Cooling, recovering the yeast, transferring it to a stainless steel barrel, alternately introducing micro-oxygen and nitrogen, performing the second stage of aging, adding an antioxidant, and obtaining a mature fermentation broth; Step S8: The mature fermentation liquid is impregnated with carbon dioxide, a clarifier is added, and the liquid is filtered, filled, and sterilized to obtain mulberry beer.

2. The process for preparing beer by fermenting fruit according to claim 1, wherein: In step S1, the oxidase is any one or more of monophenol oxidase, polyphenol oxidase, and laccase; the stirring temperature is 30-45°C, and the stirring time is 1-3 hours; the sterilization temperature is 90-95°C, and the sterilization time is 3-5 minutes; the mass ratio of mulberry, water, pectinase, and white sugar is 1:(0.55-0.72):(0.05-0.1):(0.02-0.05).

3. The process for preparing beer by fermenting fruit according to claim 1, wherein: In step S2, the malt is any one or more of barley malt and wheat malt; the temperature of the hot water is 40-50°C; the soaking time is 0.5-1h; the heating process is first boiling for 1-3 minutes, adjusting the temperature to 80-85°C, maintaining for 3-5 minutes, and then continuing to heat to 70-75°C and maintaining for 5-15 minutes; the mass ratio of the malt, hot water, and saccharifying enzyme is 1:(2-3):(0.05-0.1).

4. The process for preparing beer by fermenting fruit according to claim 1, wherein: In step S3, the temperature of the first stage fermentation is 15-20° C., and the time is 2-3 days; the amount of Pichia kluyveri is (10-30) g / L; and the volume ratio of the mulberry juice to the wort is 1:(0.2-0.5).

5. The process for preparing beer by fermenting fruit according to claim 1, wherein: In step S4, the tea leaves are any one or more of black tea, green tea, oolong tea, white tea, and dark tea; the temperature of the hot water is 70-90° C., and the mass ratio of the tea leaves to the hot water is 1:(30-60); the soaking time is 0.5-1 h; the amount of tea juice added is (100-200) mL / L; the amount of yeast extract used is (20-40) g / L; and the inoculum amount of Lactobacillus plantarum LB-1 is 1-3%.

6. The process for preparing beer by fermenting fruit according to claim 1, characterized in that: In step S4, the parameters of the ultrasonic-assisted fermentation device are set to a frequency of 20 to 30 kHz, a power of 200 to 300 W, a total ultrasonic time of 1 to 2 hours, and a duration of each ultrasonic treatment of 5 to 15 minutes; the temperature of the second stage fermentation is 20 to 25° C., and the fermentation time is 2 to 3 days.

7. The process for preparing beer by fermenting fruit according to claim 1, characterized in that: In step S5, the dosage of the Brettanomyces powder is 0.5-2 g / L; the temperature of the third stage fermentation is 18-22° C., and the fermentation time is 1-2 days.

8. The process for preparing beer by fermenting fruit according to claim 1, characterized in that: In step S6, the flow rate of the sterile air is 0.2 to 0.5 L / min; the stirring time is 10 to 30 minutes; the aging temperature is 15 to 20° C.; and the aging time is 1 to 2 days.

9. The process for preparing beer by fermenting fruit according to claim 1, characterized in that: In step S7, the temperature is lowered to 6-8°C; the antioxidant is any one or more of vitamin C, sodium erythorbate, and vitamin E; the amount of antioxidant added is (0.2-0.5) g / L; the flow rate of micro-oxygen is 0.1-0.3 L / min, and the time is 20-30 min; the flow rate of nitrogen is 0.1-0.2 L / min, and the time is 20-30 min; the temperature of the second stage aging is 0-4°C, and the aging time is 2-3 d.

10. The process for preparing beer by fermenting fruit according to claim 1, characterized in that: In step S8, the clarifier is any one or more of diatomaceous earth and edible gelatin; the amount of the clarifier is (1-5) g / L; the sterilization temperature is 70-80° C., and the sterilization time is 8-10 min; the flow rate of the carbon dioxide is 1-2 L / min, and the pressure in the barrel is 0.1-0.3 Pa; the temperature of the carbon dioxide impregnation is 22-26° C., and the impregnation time is 3-5 d.

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