Longjing craft beer and preparation method thereof

Abstract

The invention relates to the technical field of beer brewing, discloses Longjing craft beer and a preparation method thereof, and provides a synergistic process in order to solve the problems of fragrance loss, bitter taste and non-fused flavor of tea beer in the prior art. The method comprises the following steps: by taking a semi-finished Longjing tea base prepared by a specific process as a raw material, firstly saccharifying wort, and then performing low-temperature extraction to obtain a fresh taste; then, when wort is boiled, high-temperature aroma capture is performed on the brand new tea base through a condensation reflux device so as to preserve high-raising tea aroma; and finally, before the yeast is added, performing tea source pre-activation on the yeast by using the tea leaf leachate, and promoting flavor fusion through biotransformation. According to the invention, the taste and aroma of the tea leaves are integrated into the beer body step by step, the problem that the tea flavor and the beer body are difficult to balance is solved, and the prepared beer is elegant in tea aroma, fresh and refreshing in taste, free of bad bitter and astringent taste, integrated in tea, wheat and hops flavor and excellent in sensory quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of beer brewing, in particular to a Longjing craft beer and a preparation method thereof. BACKGROUND

[0002] In recent years, with the vigorous development of the craft beer market and the increasing demand of consumers for novel flavors, it has become an important innovation trend to incorporate elements with regional cultural characteristics into beer brewing. Tea, especially high-quality famous tea, has become a popular choice for brewers to try to blend flavors with beer due to its unique aroma and flavor.

[0003] However, in the existing technical practice, there are still many technical challenges in perfectly blending tea flavor with beer base. The current preparation method usually directly uses commercially available finished tea as an additive and introduces it into the brewing process through a relatively single way, such as adding during wort boiling or performing a dry-hopping-like operation during fermentation and maturation. These conventional methods have inherent defects: during high-temperature boiling, although a part of the flavor of tea can be extracted, a large amount of polyphenols, tannins and other substances in tea are dissolved, giving beer a too abrupt bitter and astringent feeling, and at the same time, the valuable and volatile aromatic substances in tea are also largely lost due to long-term high temperature, resulting in the loss of aroma of the finished product; if steeping is performed during fermentation at low temperature, although the aroma can be preserved to some extent, the extraction efficiency of the main part of the tea flavor is seriously insufficient, resulting in a thin and lack of layers of tea flavor in the final product.

[0004] Therefore, the existing technology has always been difficult to solve the balance problem between the fresh and refreshing flavor of tea, the elegant aroma and the full-bodied feeling of the wine body, and often compromises, resulting in poor integration of tea flavor and beer flavor and uncoordinated taste in the final product, making it difficult to achieve the desired quality. How to systematically and completely extract tea flavor with layers and make it harmoniously coexist with beer flavor is a technical problem to be solved in the field. SUMMARY

[0005] The purpose of the present application is to provide a Longjing craft beer and a preparation method thereof, which solves the technical defects of tea aroma loss, bitter taste and poor integration of tea flavor and wine body flavor caused by improper tea extraction in the prior art.

[0006] To achieve the above purpose, the present application is implemented by the following technical solutions: A Longjing craft beer and a preparation method thereof, the Longjing craft beer being prepared from the following raw materials: 100 parts of malt composition; 4-10 parts of semi-finished Longjing tea blank; Hops: 0.5–1.5 parts; Brewer's yeast and brewing water: as needed.

[0007] The present invention also provides a method for preparing the above-mentioned Longjing craft beer, which achieves a deep and synergistic integration of Longjing tea flavor and beer base through a series of interrelated steps.

[0008] The preparation method includes the following steps: Step 1: Preparation of semi-finished Longjing tea leaves; this step is the material basis for constructing the unique flavor system of this invention. In a preferred embodiment, fresh Longjing leaves are spread out for 2.0–4.0 hours, followed by pan-frying at 180–220°C for 8–12 minutes until the moisture content of the tea leaves reaches 30%–40%. This step intentionally stops the tea processing in an intermediate state by halting the high-temperature pan-frying process in traditional tea making. The tea leaves in this state retain more heat-sensitive fresh substances such as L-theanine, while also controlling the excessive oxidation and transformation of polyphenols, laying a unique raw material foundation for subsequent selective flavor extraction.

[0009] Step Two: Low-temperature extraction of the semi-finished Longjing tea leaves using wort; this step aims to selectively extract the main "flavor" components from the tea leaves. In a preferred embodiment, before malting and boiling, the obtained wort is contacted with the semi-finished Longjing tea leaves at 75–78°C and circulated for 15–20 minutes. This temperature range ensures the inactivation of amylase in the wort, stabilizing its components, while effectively preventing the excessive dissolution of astringent substances such as tannins at high temperatures. Utilizing the wort's own sugar, protein, and pH environment, the fresh and mellow flavor components in the tea leaves are gently extracted, completing the first construction of the flavor profile.

[0010] Step three: boiling wort and capturing high-temperature aroma during the process; this step aims to capture and replenish the "aroma" essence of tea while completing the boiling, sterilization and isomerization of hops. In a preferred embodiment, 5-10 minutes before the end of boiling, the steam generated by boiling is directed through a condensation reflux device filled with brand-new semi-finished Longjing tea blanks. The high-temperature water vapor is like a momentary steam distillation of the tea blanks, efficiently capturing the most volatile and representative fresh aroma components, and the aroma-rich condensate is then returned to the wort. This overcomes the technical defect of direct tea addition in the boiling stage, which causes a large amount of aroma loss. In this step, the malt composition can include: 80-90 parts of party pale ale malt, 5-15 parts of Munich malt, and 1-5 parts of crystal malt. Hops can also be added during boiling, such as bitter hops at the beginning of boiling and aromatic hops 10-15 minutes before the end of boiling.

[0011] Step four: tea source pre-activation of beer yeast; this step is a biological conversion bridge to achieve deep flavor fusion. It guides the metabolic direction of yeast by constructing a specific activation environment. In a preferred embodiment, beer yeast is cultured in a "tea source activation liquid". The tea source activation liquid is obtained by briefly soaking semi-finished Longjing tea blanks in sterile wort (preferably specific gravity 8.0-9.0 °P) and then filtering. The yeast is cultured in the activation liquid at 23-27°C for 8-12 hours. Specific components such as L-theanine and trace minerals in tea infusion can fine-tune the metabolic activity of yeast, guiding it to produce more flavor compounds that are more coordinated with tea flavor during subsequent fermentation, thereby achieving endogenous fusion of flavors rather than simple physical mixing.

[0012] Step five: inoculation and fermentation. This step is the link where all technical designs are finally realized. The yeast pre-activated in step four is inoculated into the wort treated in step three. In a preferred embodiment, the fermentation process includes: 7-10 days of main fermentation at 18-22°C, and 5-14 days of low-temperature aging at 0-4°C after the end of main fermentation. This fermentation and aging system provides a guarantee for the unique metabolic function of domesticated yeast and the full integration and softening of tea, malt, hop and yeast metabolites.

[0013] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application fundamentally solves the problem of poor tea beer flavor base. The specific tea blank maximally retains the fresh and refreshing flavor substances in tea leaves, while effectively controlling the components that are prone to bitterness in subsequent processing. This innovation at the raw material level lays a fresh and mellow flavor base for the final product beer, making it have significant advantages in flavor source.

[0014] 2. The low-temperature extraction step included in the present application realizes precise extraction of tea flavor substances. By processing the semi-finished Longjing tea blank under specific non-high-temperature conditions, the main body of tea fresh and mellow flavor can be selectively dissolved into wort, while avoiding the dissolution of a large amount of astringent polyphenols under high temperature. This "freshness extraction and astringency avoidance" technical feature effectively solves the technical pain point of increased bitterness and astringency when introducing tea flavor, ensuring the pure and smooth taste of beer.

[0015] 3. The present application greatly improves the aroma integrity and layering of the finished beer through the high-temperature aroma capture step added during boiling. The use of high-temperature steam for instantaneous extraction of new tea blank and the condensation of aroma backflow efficiently locks the most volatile and representative headspace aroma of Longjing tea into the beer body. This remedy makes up for the defect of easy loss of tea aroma in traditional processes, making the final product's tea aroma clear, elegant and lasting, and the aroma of the beer body interplays with it.

[0016] 4. The present application guides the yeast to produce more coordinated metabolic products with tea flavor through the use of tea infusion for pre-adaptation of yeast. This "endogenous" fusion brought by biological transformation makes tea flavor no longer an external additive, but an integral part of beer base, forming a flavor coordination and unity far beyond physical mixing.

[0017] 5. The present application ensures the excellent flavor balance and stable quality of the final product. From specific raw material processing, to segmented extraction of flavor and aroma, to biological transformation of yeast, each technical feature is indispensable. This systematic design ensures that tea flavor can be appropriately integrated into beer, neither conspicuous nor insipid, thus creating a unique style, excellent palatability and stable quality of high-end craft beer. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The present application is a method flowchart. DETAILED DESCRIPTION

[0019] The following will be combined with the Figure 1 , the present application is further explained in detail.

[0020] Example 1 The embodiment provides a preparation method of Longjing fine brewing beer, and the specific steps are as follows: (1) Raw material preparation: according to the mass fraction Preparation: 100 parts of malt composition material, containing 85 parts of party pale ale malt, 10 parts of Munich malt and 5 parts of crystal malt; 7 parts of semi-finished Longjing tea blank, 5 parts of which are used for low-temperature extraction, and 2 parts of which are used for aroma capture; 1.0 parts of hops, 0.3 parts of which are magnum hops, and 0.7 parts of which are saaz hops; Beer yeast (WLP001 California ale yeast) and brewing water in proper amounts.

[0021] (2) Preparation of semi-finished Longjing tea blank: select first-grade Longjing fresh leaves, spread for 3.0 hours. Then carry out green pot treatment in a 200°C fixation pot for 10 minutes, take out the pot when the water content of the tea leaves is about 35%, and spread and cool for standby.

[0022] (3) Preparation of wort and low-temperature extraction: crush the malt composition material in step (1), mix in a saccharification kettle according to a material-water ratio of 1:3.5, and heat to 67°C for saccharification for 68 minutes. After saccharification, the wort is pumped into an independent extraction tank, 5 parts of the semi-finished Longjing tea blank is added, and cyclic extraction is carried out at 77°C for 18 minutes. Finally, filtration, tank washing and wort combination are carried out.

[0023] (4) Boiling and aroma capture: the obtained wort is boiled for 75 minutes. At the beginning of boiling, 0.3 parts of magnum hops are added. 0.7 parts of saaz hops are added 12 minutes before the end of boiling. 8 minutes before the end of boiling, the boiling steam is passed through a condensation reflux device connected with 2 parts of brand-new semi-finished Longjing tea blank, so that the condensate is refluxed into the wort.

[0024] (5) Yeast pre-activation: part of the wort is prepared into sterile wort with a specific gravity of 8.5 °P, and then a small amount of semi-finished Longjing tea blank is added for soaking at 42°C for 25 minutes. After filtration, a tea source activation liquid is obtained. The activation liquid is cooled to 25°C, beer yeast is added, and the activation culture is carried out at the temperature for 10 hours.

[0025] (6) Fermentation and maturation: the wort in step (4) is cooled to 20°C, and the activated yeast slurry in step (5) is added. Main fermentation is carried out at 20°C for 8 days. Then, low-temperature maturation is carried out at 2°C for 10 days, finally, carbonation treatment and filling are carried out.

[0026] Example 2 The embodiment provides a preparation method of Longjing fine brewing beer, and the specific steps are as follows: (1) Raw material preparation: according to the mass fraction Preparation: 100 parts of malt composition material, containing Party pale ale malt 90 parts, Munich malt 5 parts, crystal malt 5 parts; Semi-finished Longjing tea base 4 parts, 3 parts for low-temperature extraction, 1 part for aroma capture; Hops 0.5 parts, including Magnum hops 0.2 parts and Saaz hops 0.3 parts; Beer yeast (SafAle US-05 dry beer yeast) and brewing water in appropriate amounts.

[0027] (2) Preparation of semi-finished Longjing tea base: select first-grade Longjing fresh leaves, spread for 2.0 hours. Then perform pan-firing in a pan at 180°C for 8 minutes, and take out the tea leaves when the water content is about 40%, and spread to cool for standby.

[0028] (3) Wort preparation and low-temperature extraction: crush the malt composition in step (1), mix in a saccharification kettle at a material-to-water ratio of 1:3.0, and heat to 66°C for saccharification for 60 minutes. After saccharification, pump the wort into a separate extraction tank, add 3 parts of the semi-finished Longjing tea base, and circulate for extraction at 75°C for 15 minutes. Finally, filter, wash the tank, and combine the wort.

[0029] (4) Boiling and aroma capture: boil the obtained wort for 60 minutes. At the beginning of boiling, add 0.2 parts of Magnum hops. 15 minutes before the end of boiling, add 0.3 parts of Saaz hops. 10 minutes before the end of boiling, pass the boiling steam through a condensation reflux device connected with 1 part of brand-new semi-finished Longjing tea base, and make the condensate flow back into the wort.

[0030] (5) Yeast pre-activation: prepare a portion of the wort with a specific gravity of 8.0°P, cool it to 40°C, and then add a small amount of semi-finished Longjing tea base for soaking for 20 minutes. After filtration, the tea source activation liquid is obtained. Cool the activation liquid to 23°C, add beer yeast, and activate and cultivate at this temperature for 8 hours.

[0031] (6) Fermentation and maturation: cool the wort in step (4) to 18°C, and add the activated yeast slurry in step (5). Perform main fermentation at 18°C for 7 days. Then, cool to 4°C for low-temperature maturation for 5 days, finally perform carbonation treatment and fill.

[0032] Example 3 The present embodiment provides a preparation method of Longjing craft beer, and the specific steps are as follows: (1) Raw material preparation: according to the mass fraction, Preparation: malt composition 100 parts, including: Party pale ale malt 80 parts, Munich malt 15 parts, crystal malt 5 parts; Semi-finished Longjing tea base 10 parts, of which 7 parts are used for low-temperature extraction, and 3 parts are used for aroma capture; Hops 1.5 parts, of which Magnum hops 0.5 parts, Saaz hops 1.0 parts; Beer yeast (WLP001 California Ale Yeast) and brewing water in appropriate amounts.

[0033] (2) Preparation of semi-finished Longjing tea base: Select first-grade Longjing fresh leaves, spread for 4.0 hours. Then perform pan-firing in a 220°C pan for 12 minutes, and take out the tea leaves when the water content is about 30%, and cool them down for standby use.

[0034] (3) Wort preparation and low-temperature extraction: Grind the malt composition in step (1), mix it with water in a 1:4.0 ratio in a mashing kettle, and heat it to 68°C for mashing for 75 minutes. After mashing is completed, pump the wort into a separate extraction tank, add 7 parts of the semi-finished Longjing tea base, and circulate it for extraction at 78°C for 20 minutes. Finally, filter and wash the tank, and combine the wort.

[0035] (4) Boiling and aroma capture: Boil the obtained wort for 90 minutes. At the beginning of boiling, add 0.5 parts of Magnum hops. Ten minutes before the end of boiling, add 1.0 part of Saaz hops. Five minutes before the end of boiling, pass the boiling steam through a condensation reflux device connected with 3 parts of brand-new semi-finished Longjing tea base, and make the condensate flow back into the wort.

[0036] (5) Yeast pre-activation: Prepare a portion of the wort with a specific gravity of 9.0°P, cool it to 45°C, and then add a small amount of semi-finished Longjing tea base for soaking for 30 minutes. After filtration, the tea source activation liquid is obtained. Cool the activation liquid to 27°C, and then add beer yeast for activation and cultivation at this temperature for 12 hours.

[0037] (6) Fermentation and maturation: Cool the wort in step (4) to 22°C, and then add the activated yeast slurry in step (5). Perform main fermentation at 22°C for 10 days. Then, cool it to 0°C for low-temperature maturation for 14 days, and finally perform carbonation treatment and bottling.

[0038] Comparative Example 1: Compared with Example 1, the difference is that instead of using the "semi-finished Longjing tea base" described in the present application, a commercially available finished special-grade Longjing tea that has undergone a complete pan-drying process is used as a substitute, and the total amount of tea base used is the same as that in Example 1 (7 parts). All other steps, material ratios, and process parameters are the same as in Example 1.

[0039] Comparative Example 2: Compared with Example 1, the difference is that the low-temperature extraction step in step (3) is omitted. That is, after the malt saccharification is completed, no separate low-temperature extraction process is performed, and the wort is directly filtered and the tank is washed. The amount of tea dregs used for high-temperature aroma capture in step (4) is still 2 parts, and the 5 parts of tea dregs originally used for low-temperature extraction are not used. All other steps, material ratios, and process parameters are exactly the same as in Example 1.

[0040] Comparative Example 3: Compared with Example 1, the difference is that the high-temperature aroma capture step in step (4) is omitted. That is, during the boiling of the wort, the condensation reflux device filled with tea leaves is not connected. The amount of tea dregs used for low-temperature extraction in step (3) remains unchanged, and the 2 parts of tea dregs originally used for aroma capture are not used. All other steps, material ratios, and process parameters are exactly the same as in Example 1.

[0041] Comparative Example 4: Compared with Example 1, the difference is that the temperature parameter of low-temperature extraction in step (3) is changed. The temperature of low-temperature extraction is increased from 77°C to 90°C, which is outside the range of 75-78°C of the present application. All other steps, material ratios, and process parameters are exactly the same as in Example 1.

[0042] Comparative Example 5: Compared with Example 1, the difference is that the tea source pre-activation step in step (5) is omitted. When activating the yeast, the beer yeast is directly added to the same amount of sterile wort as in Example 1, but without any tea leaf infusion liquid, and the activation temperature and time are the same as in Example 1. All other steps, material ratios, and process parameters are exactly the same as in Example 1.

[0043] Comparative Example 6: Compared with Example 1, the difference is that the amount of semi-finished Longjing tea dregs is greatly increased to verify the reasonableness of the component range. The amount of tea dregs used in low-temperature extraction in step (3) is increased to 15 parts, and the amount of tea dregs used in high-temperature aroma capture in step (4) is increased to 5 parts, with a total amount of 20 parts. All other steps, material ratios, and process parameters are exactly the same as in Example 1.

[0044] Test Example 1: Comparison of the effects of core raw materials Experimental Description This experiment aims to compare the effects of using the "semi-finished Longjing tea dregs" defined in the present application (Example 1) and using conventional commercially available finished Longjing tea (Comparative Example 1) on the content of key flavor substances in the final beer product.

[0045] 1. Sample Preparation Take 500 mL of the final product beer of Example 1 and Comparative Example 1 prepared under the same conditions and stored for the same time. Before use, perform ultrasonic degassing treatment in a 20°C water bath for 15 minutes to remove dissolved carbon dioxide.

[0046] 2. The L-theanine content test procedure is determined by high performance liquid chromatography (HPLC).

[0047] Sample pretreatment: The degassed beer sample is filtered through a 0.45 μm microporous filter membrane, and the filtrate is collected for use.

[0048] Chromatographic conditions: Chromatographic column: C18 reversed-phase chromatographic column (4.6 mm x 250 mm, 5 μm).

[0049] Mobile phase: Acetonitrile and ultrapure water, mixed at a volume ratio of 15:85.

[0050] Flow rate: 1.0 mL / min.

[0051] Column temperature: 30 °C.

[0052] Detection wavelength: 210 nm.

[0053] Quantitative method: The sample is injected into the HPLC system for analysis. By comparing with the external standard method peak area of a series of L-theanine standard solution with pre-prepared concentration gradient, the content of L-theanine in the sample is calculated, and the result is expressed in mg / L.

[0054] 3. The total polyphenol content test procedure is determined by Folin-Ciocalteu method.

[0055] Reaction procedure: 2.0 mL of degassed beer sample is accurately pipetted, 1.0 mL of Folin-Ciocalteu reagent is added, and it is thoroughly shaken and mixed, then it is left to stand for 5 minutes. Subsequently, 4.0 mL of saturated sodium carbonate solution is added, and it is again shaken and mixed.

[0056] Color development and measurement: The above mixed solution is reacted in a 40 °C constant temperature water bath for 30 minutes in the dark. After the reaction is completed, the absorbance value is measured at 765 nm wavelength using a UV-visible spectrophotometer.

[0057] Quantitative method: Gallic acid is used as the standard to make a standard curve. According to the absorbance value of the sample, the total polyphenol content in the sample is calculated from the standard curve, and the result is expressed in gallic acid equivalent (GAE) mg / L.

[0058] Experimental data Table 1 Comparison of physical and chemical indicators of finished beer of Example 1 and Comparative Example 1

[0059] Experimental summary From the test results of Table 1, it can be seen that the L-theanine content in the finished beer of Example 1 using the semi-finished Longjing tea blank defined in the present application as raw material is significantly higher than that of Comparative Example 1 using conventional finished Longjing tea, while the total polyphenol content is maintained at a low level, which is significantly lower than that of Comparative Example 1.

[0060] The above results confirm the core technical concept of the present application. The present application prepares a semi-finished Longjing tea blank by interrupting the green pot process, which aims to maximize the retention of heat-sensitive substances such as L-theanine that play a decisive role in the fresh and refreshing flavor of tea leaves. The green pot (high-temperature drying) process that conventional finished tea leaves go through inevitably leads to a large amount of degradation and loss of such substances, which is the main reason for the low L-theanine content in Comparative Example 1. This result clearly shows that the specific raw material used in the present application is the key to building a good fresh and refreshing flavor base for beer.

[0061] At the same time, the green pot process also changes the composition and state of polyphenols in tea, making it easier to dissolve substances that cause astringency and bitterness during subsequent extraction, resulting in a higher total polyphenol content in Comparative Example 1. The state of the specific raw material used in the present application not only lays a good foundation for the fresh and refreshing flavor of beer, but also controls the introduction of unpleasant flavor substances from the source, creating a key prerequisite for achieving the flavor goal of "freshness and astringency avoidance" through a specific process, thereby solving the technical problem of the difficulty in coordinating tea flavor and beer taste in the prior art.

[0062] Test Example 2: Necessity verification experiment of low-temperature extraction step Experimental description This experiment aims to verify the necessity of the low-temperature extraction step included in the present application for building the taste of the final beer product. The comparative samples are Example 1, which fully executes all steps, and Comparative Example 2, which omits the low-temperature extraction step.

[0063] 1. Sample preparation: Take 500 mL of the final finished beer of Example 1 and Comparative Example 2 prepared under the same conditions and stored for the same time. Before use, perform ultrasonic degassing treatment in a 20°C water bath for 15 minutes.

[0064] 2. L-theanine content test step: Determine by high performance liquid chromatography (HPLC).

[0065] Sample pretreatment: Filter the degassed beer sample through a 0.45μm microporous filter membrane, and collect the filtrate for use.

[0066] Chromatographic conditions: Chromatographic column: C18 reversed-phase chromatographic column (4.6mm x 250mm, 5μm).

[0067] Mobile phase: Acetonitrile and ultrapure water, mixed at a volume ratio of 15:85.

[0068] Flow rate: 1.0 mL / min.

[0069] Column temperature: 30 °C.

[0070] Detection wavelength: 210 nm.

[0071] Quantitative method: The content of L-theanine in the sample was calculated by comparing the peak area with the external standard method of L-theanine standard.

[0072] 3. Sensory evaluation (fullness of taste) procedure Panelists: 10 professional trained beer tasters.

[0073] Sample presentation: The degassed beer samples were presented to the panelists in a blind, random order at 8-10 °C.

[0074] Evaluation method: The fullness of taste of beer was evaluated using a 5-point rating scale, with the following scoring criteria: 1 point - extremely thin taste; 2 points - thin taste; 3 points - moderate taste; 4 points - full taste; 5 points - very full and rich taste.

[0075] Data processing: The average score of each group of samples was calculated.

[0076] Experimental data Table 2 Comparison of physicochemical and sensory indicators of Example 1 and Comparative Example 2

[0077] Experimental summary According to the experimental results shown in Table 2, the content of L-theanine in the finished beer and the fullness of taste score in the sensory evaluation of Example 1, which fully implements the scheme of the present application, are both significantly higher than those of Comparative Example 2, which omits the low-temperature extraction step.

[0078] This result reveals the key mechanism and indispensability of the low-temperature extraction step in the technical scheme of the present application. The core purpose of the present application, which designs the extraction of semi-finished Longjing tea blanks at 75-78 °C, is to use an accurate "temperature window" to gently and efficiently dissolve and integrate the water-soluble substances that constitute the "taste body" in tea, especially L-theanine, which imparts a fresh and refreshing sensation, into wort. Since Comparative Example 2 lacks this key step, the only source of tea flavor substances is the high-temperature aroma capture at the end of boiling, which is mainly aimed at volatile aroma components and has very low extraction efficiency for taste substances, resulting in very limited L-theanine content.

[0079] Ultimately, such differences in physicochemical indicators are directly reflected in sensory experience. The abundant L-theanine in Example 1 brings a fresh and mellow aftertaste to the beer, thus obtaining the evaluation of "full" in sensory evaluation. On the contrary, Comparative Example 2 lacks sufficient taste substance support, its taste appears thin and lacks levels, and the combination of tea flavor and beer base is on the surface. This fully proves that the low-temperature extraction step contained in the present application is a necessary technical link for building the mellow taste of the final product and realizing the deep integration of tea flavor and wine body, and is one of the core pillars for realizing the overall flavor design of the present application.

[0080] Test Example 3: Effectiveness verification experiment of high-temperature aroma capture step Experimental description The present experiment aims to verify the effectiveness of the high-temperature aroma capture step contained in the present application for fixing the characteristic aroma of tea leaves by analyzing the key volatile aroma components in the final beer product. The comparative samples are Example 1, which fully executes all steps, and Comparative Example 3, which omits the high-temperature aroma capture step.

[0081] 1. Sample preparation: Take 500 mL of the final product beer of Example 1 and Comparative Example 3 prepared and stored under the same conditions for the same time. Before use, perform ultrasonic degassing treatment in a 20°C water bath for 15 minutes.

[0082] 2. Volatile aroma component analysis step: Use headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) for analysis.

[0083] Headspace solid-phase microextraction (HS-SPME): Accurately transfer 5.0 mL of the degassed beer sample into a 20 mL headspace bottle, and add 1.5 g of sodium chloride.

[0084] Place the headspace bottle in a 60°C constant temperature water bath for 20 minutes.

[0085] Insert the aged DVB / CAR / PDMS extraction head, and adsorb at 60°C for 30 minutes.

[0086] Gas chromatography-mass spectrometry (GC-MS) analysis: Insert the adsorbed extraction head into the gas chromatography inlet, and desorb at 250°C for 5 minutes.

[0087] Chromatographic column: DB-WAX capillary column (30 m x 0.25 mm, 0.25 μm).

[0088] Temperature rising program: initial column temperature 40°C, hold for 3 minutes, rise at a rate of 5°C / min to 150°C, then rise at a rate of 10°C / min to 230°C, hold for 5 minutes.

[0089] Mass spectrometry conditions: Electron impact (EI) ion source, ion source temperature 230 °C, electron energy 70 eV, mass scan range m / z 35-450.

[0090] Component identification and quantification: The detected compounds were identified by NIST mass spectral database, and the relative content of key aroma components was compared by peak area normalization method.

[0091] Experimental data Table 3 Comparison of relative contents of key volatile aroma components in Example 1 and Comparative Example 3

[0092] Experimental summary From the experimental data in Table 3, it can be clearly seen that in the finished beer of Example 1, the relative content of linalool and geraniol, which are key compounds representing the fresh floral aroma of tea, is much higher than that of Comparative Example 3, and geraniol is even not detected in Comparative Example 3.

[0093] This significant difference strongly proves the technical mechanism and value of the high-temperature aroma capturing step in the present application. In the final stage of boiling, high-temperature steam passes through the device filled with brand-new semi-finished Longjing tea blanks, like a miniature "steam distillation", efficiently carrying out the low-boiling-point, highly volatile aromatic substances (such as linalool, geraniol, etc.) in the tea. The subsequent condensation reflux process then reintegrates these aroma-rich condensate into the main body of wort, achieving the fixation and replenishment of aroma. Comparative Example 3 lacks this step, so these valuable aroma components are either not introduced into the system or have already escaped during the long boiling process, resulting in a lack of aroma in the final product.

[0094] The overall flavor design of the present application is the synergistic construction of "taste" and "aroma". The low-temperature extraction step solves the "body" problem, while the high-temperature aroma capturing step perfectly solves the "aroma" problem. Without the aroma capturing step, as shown in Comparative Example 3, even if the beer has a certain tea taste basis, the aroma is bland and lacks the elegant and uplifting aroma characteristics of Longjing tea, resulting in incomplete tea flavor perception and obvious fault in the flavor profile. Therefore, this high-temperature aroma capturing technology is one of the key innovations of the present application that distinguishes it from the prior art, as it ensures that the final product can present a complete flavor characteristic with harmonious integration of tea aroma and body, and mutual benefit of aroma and taste.

[0095] Test Example 4: Comparison experiment of the optimization effect of low-temperature extraction process parameters Experimental description This experiment aims to demonstrate the rationality and criticality of the low extraction temperature range (75-78°C) described in the present solution. By comparing the beer prepared at the preferred temperature (Example 1) and at an out-of-range high temperature (Comparative Example 4), the differences in key indicators of mouthfeel are evaluated.

[0096] 1. Sample Preparation Take 500 mL of the final product beer of Example 1 and Comparative Example 4, which were prepared under the same conditions and stored for the same time. Before use, perform ultrasonic degassing treatment in a 20°C water bath for 15 minutes.

[0097] 2. Total Polyphenol Content Test Step Use the Folin-Ciocalteu method to determine the total polyphenol content.

[0098] Reaction Step: Accurately pipette 2.0 mL of the degassed beer sample, add 1.0 mL of Folin-Ciocalteu reagent, shake well, and let stand for 5 minutes. Then, add 4.0 mL of saturated sodium carbonate solution, and shake well again.

[0099] Color Development and Measurement: After the mixed solution is reacted in a 40°C constant-temperature water bath for 30 minutes in the dark, use a UV-visible spectrophotometer to measure its absorbance value at a wavelength of 765 nm.

[0100] Quantitative Method: Use gallic acid as the standard to prepare a standard curve, and calculate the total polyphenol content according to the absorbance value of the sample.

[0101] 3. Sensory Evaluation (Astringency Intensity) Step Panelists: A panel of 10 professionally trained beer tasters.

[0102] Sample Presentation: Present the degassed beer samples to the panelists in a blind, random order at a temperature of 8-10°C.

[0103] Evaluation Method: Use a 5-point rating scale to evaluate the "astringency intensity" of the beer, with the following scoring criteria: 1 point - no astringency; 2 points - slight astringency; 3 points - obvious astringency; 4 points - strong astringency; 5 points - extremely strong astringency with lasting astringency.

[0104] Data Processing: Calculate the average score for each group of samples.

[0105] Experimental Data Table 4 Comparison of Physicochemical and Sensory Indicators of Example 1 and Comparative Example 4

[0106] Experimental Summary As can be seen from the data in Table 4, the total polyphenol content and astringency intensity score of the final product beer of Example 1 are significantly lower than those of Comparative Example 4, which was extracted at a high temperature of 90°C.

[0107] This result clearly reveals the setting mechanism of the low temperature extraction temperature window in the present application. The chemical composition of tea is complex, and the dissolution rates of different substances are greatly different at different temperatures. The present application controls the extraction temperature at 75-78°C, and the core is to perform "selective extraction". At this temperature, small molecule substances such as L-theanine that constitute the fresh and refreshing taste can be efficiently dissolved, while the dissolution of polyphenols such as tannins with large molecular weight and easy to produce astringency is effectively inhibited. In Comparative Example 4, the temperature is increased to 90°C, although more tea substances can be extracted, but this extraction is indiscriminate, resulting in a large amount of astringent polyphenols affecting the taste entering the wort, thereby causing the total polyphenol content to increase sharply.

[0108] The difference in physical and chemical indicators ultimately determines the pros and cons of sensory quality. Comparative Example 4 has a very strong astringency in sensory evaluation due to the excessively high total polyphenol content, and this rough convergence seriously damages the drinkability of beer and masks other pleasant flavors. While Example 1 has a refreshing taste and a smooth entry, the fresh and refreshing taste of tea coexists harmoniously with the richness of malt. This proves that the precise control of the extraction temperature in the present application is the key to solving the technical problem of balancing "tea flavor" and "astringency" in tea beer, and is the technical guarantee for achieving the goal of "fresh and refreshing without bitterness", rather than a parameter that can be adjusted at will.

[0109] Test Example 5: Verification experiment of the biological conversion effect of the yeast tea source pre-activation step Experimental description This experiment aims to verify the contribution of the "yeast tea source pre-activation" step in the present application scheme to the final beer flavor system. By comparing Example 1 using this step with Comparative Example 5 using the conventional activation method, the differences in key flavor substance generation and overall flavor sensory are evaluated.

[0110] 1. Sample preparation Take 500 mL of the final product beer of Example 1 and Comparative Example 5 prepared under the same conditions and stored for the same time. Before use, perform ultrasonic degassing treatment in a 20°C water bath for 15 minutes.

[0111] 2. Analysis of characteristic ester substances The analysis is performed using headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) technology.

[0112] Headspace solid phase microextraction (HS-SPME): Accurately transfer 5.0 mL of the degassed beer sample into a 20 mL headspace bottle, add 1.5 g of sodium chloride, and seal.

[0113] Place the headspace bottle in a 60°C constant temperature water bath for 20 minutes.

[0114] Insert the aged DVB / CAR / PDMS extraction head into the headspace and adsorb for 30 min at 60 °C.

[0115] Gas chromatography-mass spectrometry (GC-MS) analysis: Insert the adsorbed extraction head into the gas chromatography injection port, desorb at 250 °C for 5 min for analysis.

[0116] Chromatographic column: DB-WAX capillary column (30 m x 0.25 mm, 0.25 μm).

[0117] Temperature program: initial column temperature 40 °C, hold for 3 min, increase at a rate of 5 °C / min to 150 °C, then increase at a rate of 10 °C / min to 230 °C, hold for 5 min.

[0118] Mass spectrometry conditions: electron impact (EI) ion source, electron energy 70 eV, mass scan range m / z 35-450.

[0119] Component identification and quantification: the detected compounds were identified by NIST mass spectrometry database, and the relative content of key ester aroma components produced by yeast metabolism was compared by peak area normalization method.

[0120] 3. Sensory evaluation (flavor fusion) steps Panel: composed of 10 professional trained beer tasters.

[0121] Sample presentation: the degassed beer samples were presented to the panel in a blind, random order at 8-10 °C.

[0122] Evaluation method: a 5-point rating scale was used to evaluate the "flavor fusion and coordination" of beer, with the following scoring criteria: 1 point - flavor completely separated, tea flavor and beer flavor conflict; 2 points - flavor separation; 3 points - flavor is basically coordinated; 4 points - good flavor fusion; 5 points - perfect flavor fusion, integrated.

[0123] Data processing: calculate the average score of each group of samples.

[0124] Experimental data Table 5 Comparison of key esters and sensory indicators of Example 1 and Comparative Example 5

[0125] Experimental summary The experimental data in Table 5 shows that the relative content of isoamyl acetate and ethyl acetate, which are produced by yeast metabolism and can bring pleasant fruity aroma, in the finished beer of Example 1 is significantly higher than that of Comparative Example 5. This chemical difference is ultimately reflected in the sensory evaluation, and the score of Example 1 in "flavor integration" is much higher than that of Comparative Example 5.

[0126] This result profoundly reveals the biological mechanism and technical value of the "yeast tea source pre-activation" step. In Comparative Example 5, the yeast is activated in the conventional wort, and the subsequent fermentation produces a standard metabolic product profile. The core innovation of the present application is that the yeast in Example 1 is "pre-activated" in a specific environment containing the semi-finished Longjing tea blank leaching solution. This process not only restores the activity of the yeast, but more importantly, it uses L-theanine, trace elements and other specific components in the tea leaf leaching solution to "pre-guide" or "domesticate" the metabolic pathways of the yeast, so that it tends to generate more or different proportions of ester compounds in the subsequent main fermentation environment.

[0127] The flavor enhancement brought about by biological transformation is fundamentally different from simple physical mixing. The flavor of Comparative Example 5 is more like a direct superposition of beer and tea soup, and there is a certain sense of separation in the sense of organoleptic. In Example 1, the "domesticated" yeast produces more ester compounds, which, like a chemical "bridge", organically connects the richness of malt, the bitterness of hops and the elegance of tea leaves, forming a highly integrated composite flavor system that cannot be achieved by simple blending. The "integrated whole" given by the sensory evaluation team is a direct affirmation of this "endogenous" flavor integration, and also proves the indispensability of this biological transformation step for achieving the ultimate flavor goal of the present application.

[0128] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A Longjing craft beer, characterized in that, It is prepared from the following raw materials in the quality parts: Malt composition material: 100 parts; Half-finished Longjing tea base: 4-10 parts; Hops: 0.5-1.5 parts; Beer yeast and brewing water: appropriate amount.

2. A method of preparing a Longjing Craft Beer according to claim 1, characterized in that, It comprises the following steps: Step one: preparation of half-finished Longjing tea base; Step two: low-temperature extraction of the half-finished Longjing tea base with wort to obtain wort containing tea flavor; Step three: boiling of the wort containing tea flavor and aroma capture of brand-new half-finished Longjing tea base with high-temperature steam during boiling to make the aroma condensate backflow into the wort; Step four: pre-activation of beer yeast with activation liquid containing half-finished Longjing tea base leaching liquid; Step five: inoculation of the pre-activated yeast into the wort obtained in step three for fermentation.

3. The preparation method according to claim 2, characterized in that, The step one is specifically: spreading Longjing fresh leaves for 2.0-4.0 hours, and then conducting green pot treatment at 180-220°C for 8-12 minutes, stopping when the tea leaf moisture content is 30%-40% to obtain the half-finished Longjing tea base.

4. The preparation method according to claim 2, characterized in that, The wort is obtained by saccharification of malt composition material, and the malt composition material comprises: 80-90 parts of party pale ale malt, 5-15 parts of Munich malt and 1-5 parts of crystal malt.

5. The preparation method according to claim 2, characterized in that, The low-temperature extraction in step two is specifically: contacting and circulating extraction of wort with the half-finished Longjing tea base at a temperature of 75-78°C for 15-20 minutes before the end of malt saccharification and the beginning of boiling.

6. The preparation method according to claim 2, characterized in that, The aroma capture in step three is specifically: passing the steam generated during boiling through a condensate backflow device filled with the half-finished Longjing tea base 5-10 minutes before the end of boiling to make the condensate carrying tea aroma backflow into the wort.

7. The preparation method according to claim 2, characterized in that, The pre-activation in step four specifically comprises: preparing tea source activation liquid and culturing beer yeast to be used in the tea source activation liquid.

8. The preparation method according to claim 7, characterized in that, The preparation method of the tea source activation liquid is: putting the half-finished Longjing tea base into sterile wort with a specific gravity of 8.0-9.0 °P for soaking, and then removing the tea leaves by filtration to obtain; the culture conditions are: activation at 23-27°C for 8-12 hours.

9. The preparation method according to claim 2, characterized in that, The boiling process in step three also comprises the step of adding hops, specifically: adding bitter hops at the beginning of boiling and adding aromatic hops 10-15 minutes before the end of boiling.

10. The method of claim 2, wherein, The fermentation in step five comprises: main fermentation at 18-22°C for 7-10 days, and low-temperature aging at 0-4°C for 5-14 days after the end of main fermentation.

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