Preparation method of Longjing tea beer

Abstract

The invention relates to a preparation method of Longjing tea beer, which comprises the following steps: 1) crushing malt, adding water, carrying out gradient heating saccharification to obtain wort, boiling the wort, adding hops, cooling, and inoculating yeast into the cooled wort for fermentation; 2) taking Longjing tea for pretreatment, putting the pretreated tea leaves into an extraction tank, and extracting by adopting a low-temperature circulating extraction mode to obtain tea-containing beer fermentation liquor; and (3) fully and uniformly mixing the tea-containing beer fermentation liquor obtained by low-temperature circulating extraction, and carrying out membrane filtration, sterilization and filling to obtain the Longjing tea beer finished product. Characteristic flavor substances in the Longjing tea are extracted into the beer in a low-temperature circulating extraction mode, bitterness of the beer is avoided, the extraction rate of nutritional ingredients is increased, the sterilization and aroma enhancement effects are achieved in the mode that tea leaves are subjected to heat treatment before soaking, and the Longjing tea beer has the advantages of being obvious in Longjing characteristic flavor, stable in quality, rich in nutrition and the like; the method is suitable for large-scale preparation of Longjing tea beer products.

Description

Technical Field

[0001] The invention belongs to the technical field of beer processing, and particularly relates to a method for preparing Longjing tea beer. Background Art

[0002] Tea beer is a new type of beer with both tea and beer flavors obtained by adding tea or tea extracts during the beer preparation process. In recent years, the tea beer market has developed rapidly, with a wide range of products such as Longjing wheat beer, Anji white tea wheat beer, and jasmine tea wheat beer. However, the flavor of tea is easily masked by beer, and some products even enhance the flavor of tea by adding flavors, which makes it difficult to meet consumer demand. Therefore, how to highlight the tea flavor in beer has become one of the technical difficulties in the preparation of tea beer.

[0003] The flavor substances of tea mainly include tea polyphenols, amino acids, caffeine, enols, esters and other ingredients. Although the traditional hot extraction method of tea can quickly extract the nutrients in the tea, the bitter substances are also quickly extracted, resulting in a strong bitter taste in tea beer. Although cold extraction of tea can reduce the extraction of bitter substances, the effective ingredients of tea are not fully extracted, and there is also a greater risk of contamination by foreign bacteria. Therefore, avoiding bitterness and foreign bacterial contamination during the process of blending tea into beer is another technical difficulty that needs to be solved in the preparation of tea beer.

[0004] In view of the above technical difficulties, the present invention, on the one hand, adopts a low-temperature circulation extraction method to extract the characteristic flavor substances in Longjing tea into beer and avoid its bitterness, thereby improving the extraction rate of nutrient components. On the other hand, it also adopts a method of pre-heat treatment of tea leaves before immersion, which not only sterilizes the tea leaves, but also enhances the aroma of the tea leaves. The technical solution provided by the present invention makes Longjing tea beer have the advantages of obvious Longjing characteristic flavor, stable quality, rich nutrition, etc., and is suitable for large-scale preparation of Longjing tea beer products. Summary of the invention

[0005] In view of the problems of unclear tea flavor and poor stability in the existing tea beer preparation technology, the present invention provides a method for preparing Longjing tea beer, which can prepare Longjing tea beer products with obvious Longjing characteristic flavor, stable quality and rich nutrition at a relatively low cost, and is specifically achieved through the following technical solutions: A method for preparing Longjing tea beer, the method comprising the following steps: 1) The malt is crushed, and after adding water, it is saccharified by gradient temperature rise. The saccharified mash is filtered to obtain wort, the wort is boiled, hops are added for the first time, and after boiling for 60 minutes, hops are added for the second time, and then cooled. Yeast is inoculated into the cooled wort for fermentation; 2) Pre-treating Longjing tea leaves, placing the pre-treated tea leaves in an extraction tank, and extracting the tea leaves by a low-temperature circulation extraction method to obtain tea-containing beer fermentation liquid; 3) The tea beer fermentation liquids obtained by low-temperature circulation extraction are fully mixed, and the finished Longjing tea beer is obtained by membrane filtration, sterilization and filling.

[0006] Furthermore, in step 1), the conditions of yeast fermentation are: main fermentation at 16-20°C for 5-7 days, then gradually cooling to 4°C and maintaining for 15-30 days until the diacetyl in the fermentation liquid drops below 0.1 mg / L.

[0007] Furthermore, in step 2), the Longjing tea pretreatment is specifically heat-treating the Longjing tea leaves in an oven at 75-85° C. for 1-2 h.

[0008] Furthermore, in step 2), the low-temperature cyclic extraction is specifically as follows: a portion of the beer fermentation liquid is pumped into the extraction tank to extract the tea leaves, the extraction temperature is controlled at 0-4°C, the extraction time is 6-8h, and after a single extraction, the tea-containing beer fermentation liquid is filtered out of the extraction tank; then the beer fermentation liquid is pumped into the extraction tank for extraction again, and the extraction is cyclically performed 3-5 times.

[0009] The present invention innovatively proposes a low-temperature circulating extraction method for preparing Longjing tea beer. Since high temperature can easily extract bitter substances in tea leaves, the tea beer has a very strong bitter taste. Although low-temperature extraction can reduce the dissolution of bitter substances, the extraction rate is also low, and there is a certain risk of bacterial contamination. The low-temperature circulating extraction method provided by the present invention can not only greatly improve the extraction rate of tea flavor substances, but also avoid the excessive bitterness of tea beer. In order to avoid the problem of microbial contamination in low-temperature extracted tea leaves, the present invention also adopts a method of heat-treating the tea leaves before immersion, which not only sterilizes the tea leaves, but also enhances the aroma of the tea leaves. Therefore, the method provided by the present invention can highlight the tea flavor in tea beer.

[0010] The Longjing tea beer product produced by the technical solution provided by the present invention has the advantages of obvious Longjing tea characteristic flavor, stable quality, rich nutrition, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Comparison of catechin content in beer prepared in the examples of the present invention and the comparative example; Figure 2 The figure shows a comparison of the sensory qualities of three beers prepared in the embodiments of the present invention and the control examples. DETAILED DESCRIPTION

[0012] The present invention is further described below in conjunction with specific embodiments to facilitate a better understanding of the present technical solution.

[0013] Example 1: Preparation of Longjing Tea Beer by Low-Temperature Circulation Extraction The malt was crushed, and water was added in a ratio of 1:5 to make a mash. The saccharification was carried out by step-wise heating, from 40℃ to 78℃, and the total saccharification was 80 min. After the saccharification was completed, it was filtered, and the spent grains were washed 3-5 times after being filtered. The wort was boiled, and 0.1 g / L of hops was added for the first time; after boiling for 60 min, 0.3 g / L of hops was added for the second time, and cooled. Yeast was inoculated into the cooled wort, and the main fermentation was carried out at 16℃ for 7 days. Then the temperature was gradually lowered to 4℃ and maintained for 30 days until the diacetyl in the fermentation liquid dropped below 0.1 mg / L.

[0014] Longjing tea was pretreated in an oven at 75 ℃ for 2 h, and then the pretreated tea was added to the extraction tank at a dosage of 5 g / L (calculated based on the volume of beer fermentation liquid). Longjing tea was extracted by low-temperature circulation extraction: 20% beer fermentation liquid was pumped from the fermentation tank into the extraction tank to extract the pretreated tea, the extraction temperature was controlled at 4 ℃, the extraction time was 6 h, and after a single extraction, the tea-containing beer fermentation liquid was filtered out of the extraction tank; then 20% beer fermentation liquid was pumped into the extraction tank for re-extraction, and the extraction was circulated for 5 times. The tea-containing beer fermentation liquid obtained by low-temperature circulation extraction was fully mixed, and the low-temperature circulation extraction Longjing tea beer product was obtained by membrane filtration, sterilization and filling.

[0015] Comparative Example 1: Preparation of control beer The malt was crushed, water was added in a ratio of 1:5, and the mash was prepared. The saccharification was carried out by step-wise heating, from 40°C to 78°C, and the total saccharification was 80 min. After the saccharification was completed, the saccharification was carried out by filtration, and the spent grains were washed 3-5 times after filtration. The wort was boiled, and 0.1 g / L hops were added for the first time; after boiling for 60 min, 0.3 g / L hops were added for the second time, and cooled. Yeast was inoculated in the cooled wort, and the main fermentation was carried out at 16°C for 7 days. Then the temperature was gradually lowered to 4°C and maintained for 30 days until the diacetyl in the fermentation liquid dropped below 0.1 mg / L. The control beer sample was obtained by membrane filtration, sterilization and filling.

[0016] Comparative Example 2: Preparation of hot-extracted Longjing tea beer The malt was crushed, water was added in a ratio of 1:5, and the mash was prepared. The saccharification was carried out by step-wise heating, gradually increasing the temperature from 40℃ to 78℃, and the total saccharification was 80 min. After the saccharification was completed, the saccharification was carried out by filtering, and the slag was washed 3-5 times after filtering. The wort was boiled, and 0.1 g / L hops were added for the first time; after boiling for 60 min, 0.3 g / L hops were added for the second time; after cooling to 85℃, 5 g / L Longjing tea was added for hot extraction for 20 min. After the tea extraction was completed, the wort was cooled to 16℃. Yeast was inoculated in the cooled wort, and the main fermentation was carried out at 16℃ for 7 days. After that, the temperature was gradually lowered to 4℃ and maintained for 30 days until the diacetyl in the fermentation liquid dropped below 0.1mg / L. The hot-extracted Longjing tea beer sample was obtained by membrane filtration, sterilization and filling.

[0017] Verification Example 1 Catechins are important quality components in tea. Catechins in three kinds of beers were determined by high performance liquid chromatography: the detector was an ultraviolet detector with a detection wavelength of 280 nm. Mobile phase: A was 2% acetic acid, and mobile phase B was pure acetonitrile. Gradient elution was used: 0-16 min, mobile phase B increased linearly from 6.5% to 15%; 16-25 min, mobile phase B increased linearly from 15% to 25%; 25-30 min, mobile phase B decreased linearly from 25% to 6.5%; 30-35 min, mobile phase B was constant at 6.5%. The flow rate was 1 mL / min, the column temperature was 40 ℃, and the injection volume was 10 μL. Standard solutions were prepared with eight catechin standards, and standard curves of standard concentration and peak area were drawn. The concentration of each component was calculated by the peak area of ​​the sample.

[0018] The results of catechins are as follows Figure 1 As shown in the figure, only one catechin was detected in the control group, with a content of only 2.1 mg / L, which means that the catechin content in ordinary beer is very low. The total amount of catechins in the hot extraction group was 228.1 mg / L, while the total amount of catechins in the low temperature cyclic extraction group was 199.3 mg / L. Although the total amount of catechins in the low temperature cyclic extraction group was slightly lower than that in the hot extraction group, it was much higher than that in the control group.

[0019] Verification Example 2 The sensory qualities of the three beer samples were compared in terms of aroma, taste, tea flavor, and malt flavor. Figure 2As shown. In terms of aroma, the scores of the three beer samples ranged from 5.5 to 7.0, among which the aroma score of the C low-temperature circulation extraction group was the highest, while the aroma score of the control group was the lowest. The taste scores of the three beer samples ranged from 6.0 to 7.8, among which the taste score of the low-temperature circulation extraction group was the highest, while the taste score of the control group was the lowest. The tea flavor score of the control group was 0, indicating that there was no tea flavor in the control beer; the tea flavor scores of the hot extraction group and the low-temperature circulation extraction group were 1.5 and 3.5, respectively, indicating that the low-temperature circulation extraction group can significantly improve the tea flavor of tea beer. In terms of malt flavor, the highest score of the control group was 4.0, while the scores of the hot extraction group and the low-temperature circulation extraction group were 3.0 and 3.5, respectively. Overall, the aroma, taste and tea flavor scores of the samples in the low-temperature circulation extraction group were the highest, and the malt flavor was second only to the control group. Therefore, compared with the hot extraction group, the low-temperature circulation extraction group is more helpful in improving the sensory quality of Longjing tea beer.

Claims

1. A method for preparing Longjing tea beer, characterized in that: The preparation method comprises the following steps: 1) The malt is crushed, and after adding water, it is saccharified by gradient temperature rise. The saccharified mash is filtered to obtain wort, the wort is boiled, hops are added for the first time, and after boiling for 60 minutes, hops are added for the second time, and then cooled. Yeast is inoculated into the cooled wort for fermentation; 2) Pre-treating Longjing tea leaves, placing the pre-treated tea leaves in an extraction tank, and extracting the tea leaves by a low-temperature circulation extraction method to obtain tea-containing beer fermentation liquid; 3) The tea beer fermentation liquids obtained by low-temperature circulation extraction are fully mixed, and the finished Longjing tea beer is obtained by membrane filtration, sterilization and filling.

2. The method for preparing Longjing tea beer according to claim 1, characterized in that In step 1), the yeast fermentation conditions are: main fermentation at 16-20°C for 5-7 days, then gradually cooling to 4°C and maintaining for 15-30 days until the diacetyl in the fermentation liquid drops below 0.1 mg / L.

3. The method for preparing Longjing tea beer according to claim 1, characterized in that In step 2), the Longjing tea pretreatment is specifically to heat-treat the Longjing tea leaves in an oven at 75-85°C for 1-2 h.

4. The method for preparing Longjing tea beer according to claim 1, characterized in that In step 2), the low-temperature cyclic extraction is specifically as follows: pumping part of the beer fermentation liquid into the extraction tank to extract the tea leaves, controlling the extraction temperature to 0-4°C, the extraction time to 6-8h, filtering the tea-containing beer fermentation liquid out of the extraction tank after a single extraction; then pumping the beer fermentation liquid into the extraction tank for another extraction, and cyclically extracting for 3-5 times.

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