A method for preparing high-tf-content black tea by combining cyclic light curing and exogenous complex enzyme oxidation

Abstract

The application discloses a method for preparing high TF content black tea by combining cyclic light wilting with exogenous complex enzyme oxidation, and the method is characterized in that the high TF content black tea is prepared from fresh leaves with a bud and two leaves, which are used as raw materials, and have an EC content higher than 2.0%, an EGC content higher than 3.0% and a total catechin content higher than 15.0%, and are processed through seven procedures of cyclic light wilting by a wilting machine, complex enzyme treatment, green tea shaking, rolling, de-blocking, fermentation and drying. The method can reduce the bitterness and astringency of black tea by regulating the substrate for the formation of theaflavins of the raw materials, and can control the formation and accumulation of theaflavins in the processing of black tea by adding complex enzymes and matching low-temperature fermentation technology, so that a high TF content black tea with a theaflavin content higher than 0.35% is finally prepared. The process can be widely applied to the field of black tea processing and improves the utilization rate of summer and autumn tea.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of black tea processing, and particularly relates to a method for preparing high-TF-content black tea by combining cyclic light wilting with exogenous composite enzyme oxidation. BACKGROUND

[0002] Summer and autumn tea has high content of tea polyphenols and low content of amino acids, and thus is not suitable for making green tea with good quality, but is a high-quality raw material for processing black tea. Processing summer and autumn tea into black tea is the most direct method for improving the utilization rate of summer and autumn tea, and a suitable processing technology needs to be matched.

[0003] Theaflavins are important components in black tea and are positively correlated with the quality of black tea. During the fermentation of black tea, catechins are oxidized by enzymes to form theaflavins, but theaflavins are not stable and will continue to be oxidized and polymerized to form thearubigins and theabrownins, which are higher-polymerized products. Therefore, as an intermediate product, it is difficult to improve the content of theaflavins. TF is one of the four main theaflavins in tea leaves and is the component with the lowest bitterness and astringency among the four theaflavins, and is significantly positively correlated with the brightness of the soup color of black tea. Exogenous enzyme addition is an important way to improve the content of theaflavins in black tea. The present application has found that the combination of tanninase and pectinase has great potential to improve the content of theaflavins in black tea, but is affected by tea varieties, picking time, bud leaf tenderness, wilting method, fermentation conditions and other conditions. Therefore, how to optimize the fresh leaf raw material and processing technology to finally obtain high-TF-content black tea is the main purpose of the present application. SUMMARY

[0004] The present application is designed to provide a method for preparing high-TF-content black tea by combining cyclic light wilting with exogenous composite enzyme oxidation, and to provide a new processing idea for the research and development of black tea products. The technical scheme is as follows:

[0005] The method for preparing high-theaflavin black tea by combining cyclic light wilting with exogenous enzyme oxidation comprises the following steps:

[0006] Step 1: The tea fresh leaves have a tenderness of one bud and two leaves, are picked in May to July, and meet the requirements of catechin composition content, i.e., the EC content is higher than 2.0%, the EGC content is higher than 3.0%, and the total catechin content is higher than 15.0%. Limiting the picking time, tenderness and catechin content of the fresh leaves is a basic condition for processing high-theaflavin black tea.

[0007] Step two, adopt the wilt machine to carry out the cycle light wilting, spread the tea fresh leaves on the wilt machine, the leaf thickness is 2-4cm, the wilt machine is multi-layer structure, the uppermost layer is the light layer, supplement the white light source, the light intensity is 2000-3000Lx, the wilt machine can realize the cycle turning of the upper and lower layers of tea leaves with the track movement, the light and dark alternating times are 3-5 times, the light and dark alternating times are 3-5 times. The wilting degree is that the wilting leaf moisture content reaches 62-65%. The wilt machine is used for cycle light wilting, on the one hand, the wilting efficiency is improved by partial light supplement, the light and dark alternation is helpful for water and sun, so that the leaf and stem lose water uniformly, on the other hand, the cycle light wilting improves the polyphenol oxidase activity, which is beneficial to the oxidation of catechin to form theaflavins.

[0008] Step three, add enzyme treatment to add exogenous tannase and pectinase complex enzyme solution, the mass ratio of adding complex enzyme to tea fresh leaves is 1:500-1:1000, the ratio of tannase to pectinase in complex enzyme is 1:1-3:1, the complex enzyme treatment method is to dissolve with pure water first, the solid-liquid ratio is 1:5-1:20, after dissolution, the supernatant is uniformly sprayed on the tea leaves in the form of mist droplets. The enzyme addition link is the key step of preparing tea theaflavins black tea, which improves the content of theaflavins in black tea by improving the efficiency of enzyme oxidation and directional oxidation pathway.

[0009] Step four, put the enzyme-added tea leaves into the rolling machine, set the rotating speed to 15-30r / min, and the rolling time is 60-90min. The rolling treatment is different from that of oolong tea and floral red tea, the main purpose is to mix the enzyme solution and wilted leaves evenly, and to break the wilted leaf cells by slow rolling, so that the enzyme solution and catechin can be fully contacted, at the same time, the rolling can also lose part of the water, which is convenient for subsequent rolling.

[0010] Step five, adopt the rolling machine to roll, the rolling time is 50-70min, the pressure mode is "light-heavy-light", the light pressure time is 5-10min, the heavy pressure time is 40-50min, and the last light pressure time is 5-15min.

[0011] Step six, use the de-blocking machine to de-block, the conventional de-blocking process is not described in detail.

[0012] Step seven, adopt low-temperature fermentation, the fermentation temperature is 15-20℃, and the fermentation time is 2-3 hours. Low-temperature fermentation is the key to ensure the accumulation of theaflavins during fermentation, which is different from the conventional fermentation above 30℃, and the fermentation time is shortened after enzyme treatment, which can be completed in 2-3 hours.

[0013] Step eight, the tea leaves after fermentation are dried by two-step drying method of rough fire and full fire, the rough fire temperature is 110-130 DEG C, the time is 8-15 min, the full fire temperature is 60-80 DEG C, and the time is 60-90 min.

[0014] The high theaflavins black tea processing method of the application uses fresh leaves of a variety with EC content higher than 2.0%, EGC content higher than 3.0%, and total catechin content higher than 15.0%, with one bud and two leaves, and picked in May to July as raw materials, and is processed through seven procedures of machine circulation light wilting, enzyme addition, rolling, rubbing, de-blocking, fermentation and drying. The machine circulation light wilting improves the wilting efficiency through part of the light circulation, and realizes the balance of rapid water loss and water removal, and improves the polyphenol oxidase activity through the circulation light wilting, and accelerates the oxidation of catechin to form theaflavins. The enzyme addition is the key of the application, the addition of the tannase and pectinase compound solution to the wilted leaves improves the enzyme oxidation efficiency and the directional oxidation pathway to improve the TF content of the black tea. The subsequent rolling process breaks the wilted leaf cells, and makes the enzyme solution fully contact with the catechin, and the rolling also removes part of the water, which is convenient for the subsequent rubbing. The fermentation conditions are adjusted, the low-temperature short-time fermentation method is adopted, the fermentation temperature is 15-20 DEG C, the fermentation time is 2-3 hours, the accumulation of TF in the fermentation process of the black tea is improved, and finally the high theaflavins black tea is dried. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme of the application is clearly and completely described below in combination with specific examples.

[0016] Example 1

[0017] 1) Fresh leaf picking: the golden bud variety is selected, the picking time is in June, and the picking tenderness is one bud and two leaves (EC content 2.1%, EGC content higher than 4.2%, and total catechin content higher than 17.5%);

[0018] 2) Circulation light wilting: the wilting machine is used for light supplement wilting, the fresh tea leaves are thinly spread on the wilting machine, the leaf thickness is 2-4 cm, the uppermost layer of the wilting machine is the light layer, the white light source is supplemented, the light intensity is 2200-2500 Lx, and the wilting machine can realize the circulation of the upper and lower layers of the tea leaves through the movement of the caterpillar. The wilting degree is that the moisture content of the wilted leaves reaches 62-64%, the ratio of light time to dark time is 1:4, and the light and dark are alternated for 4 times.

[0019] 3) Enzyme addition: Add exogenous tanninase and pectinase complex enzyme solution, the mass ratio of added complex enzyme to tea fresh leaves is 1:600-1:900, the ratio of tanninase to pectinase in the complex enzyme is 1:1-3:1, the complex enzyme treatment method is to dissolve it with pure water first, the solid-liquid ratio is 1:5-1:20, after dissolution, centrifuge at 5000 rpm for 10 min, and then evenly spray the supernatant in the form of mist droplets on the tea leaves.

[0020] 4) Rolling: Put the wilted leaves with added enzyme into the rolling machine, set the rotating speed to 15-20 rpm, and the rolling time to 70-80 min.

[0021] 5) Rolling: Use the rolling machine to roll, the rolling time is 50-70 min, the pressure mode is "light-heavy-light", among which the light pressure time is 5-10 min, the heavy pressure time is 40-50 min, and the final light pressure time is 5-15 min.

[0022] 6) Deblocking: Deblock the rolled leaves with a deblocking machine;

[0023] 7) Fermentation: Use low-temperature fermentation method, the fermentation temperature is 16-18℃, and the fermentation time is 2-3 hours.

[0024] 8) Drying: Use two-step drying method of rough fire and full fire, the rough fire temperature is 110-130℃, the time is 8-15 min, the full fire temperature is 60-80℃, and the time is 60-90 min.

[0025] The TF content of the black tea sample processed in this example is 0.40-0.50%.

[0026] Comparative Example

[0027] Example 2

[0028] 1) Fresh leaf picking: Select Longjing 43 variety, pick in June, and pick the tenderness of one bud and two leaves (EC content 2.0%, EGC content 3.5%, total catechin content 17.5%);

[0029] 2) Circulating light wilting: Use a wilting machine for light supplement wilting, spread the tea fresh leaves on the wilting machine, the leaf thickness is 2-4 cm, the uppermost layer of the wilting machine is the light layer, supplemented by white light source, the light intensity is 2200-2500 Lx, the wilting machine can realize the circulation of the upper and lower layers of tea leaves with the movement of the track, the ratio of light time to dark time is 1:4, and the light and dark alternate 4 times. The wilting degree is that the moisture content of wilted leaves reaches 62-64%.

[0030] 3) adding enzyme: adding exogenous tanninase and pectinase complex enzyme solution, the mass ratio of added complex enzyme to tea fresh leaves is 1:600-1:900, the ratio of tanninase to pectinase in the complex enzyme is 1:1-3:1, the complex enzyme treatment method is to dissolve it fully with pure water, the solid-liquid ratio is 1:5-1:20, after dissolving, centrifugation is carried out at 5000 r / min for 10 min, and the supernatant is uniformly sprayed on the tea leaves in the form of mist droplets.

[0031] 4) shaking: putting the wilted leaves with added enzyme into a shaking machine, setting the rotating speed to 15-20 r / min, and shaking for 70-80 min.

[0032] 5) rolling: rolling is carried out by using a rolling machine, the rolling time is 50-70 min, the pressure mode is "light-heavy-light", the light pressure time is 5-10 min, the heavy pressure time is 40-50 min, and the final light pressure time is 5-15 min.

[0033] 6) deblocking: deblocking the rolled leaves by using a deblocking machine;

[0034] 7) fermentation: low-temperature fermentation is adopted, the fermentation temperature is 16-18℃, and the fermentation time is 2-3 hours.

[0035] 8) drying: two-step drying method of rough fire and full fire is adopted, the rough fire temperature is 110-130℃, the time is 8-15 min, the full fire temperature is 60-80℃, and the time is 60-90 min.

[0036] The TF content of the black tea sample processed in this example is 0.35-0.45%.

[0037] Example 3

[0038] 1) picking fresh leaves: selecting Longjing 43 variety, picking time is in June, and the picking tenderness is one bud and two leaves (EC content is 2.0%, EGC content is 3.5%, and total catechin content is 17.5%);

[0039] 2) wilting: natural wilting, spreading on a wilting rack, and the wilting degree is that the water content of wilted leaves reaches 62-64%.

[0040] 3) adding enzyme: adding exogenous tanninase and pectinase complex enzyme solution, the mass ratio of added complex enzyme to tea fresh leaves is 1:600-1:900, the ratio of tanninase to pectinase in the complex enzyme is 1:1-3:1, the complex enzyme treatment method is to dissolve it fully with pure water, the solid-liquid ratio is 1:5-1:20, after dissolving, centrifugation is carried out at 5000 r / min for 10 min, and the supernatant is uniformly sprayed on the tea leaves in the form of mist droplets.

[0041] 4) Rolling: put the wilted leaves with enzyme into the rolling machine, set the rotating speed at 15-20 rounds / min, and the rolling time at 70-80 min.

[0042] 5) Rolling: put the wilted leaves with enzyme into the rolling machine, set the rotating speed at 15-20 rounds / min, and the rolling time at 70-80 min.

[0043] 6) Rolling: put the wilted leaves with enzyme into the rolling machine, set the rotating speed at 15-20 rounds / min, and the rolling time at 70-80 min.

[0044] 7) Rolling: put the wilted leaves with enzyme into the rolling machine, set the rotating speed at 15-20 rounds / min, and the rolling time at 70-80 min.

[0045] 8) Rolling: put the wilted leaves with enzyme into the rolling machine, set the rotating speed at 15-20 rounds / min, and the rolling time at 70-80 min.

[0046] The TF content of the black tea sample processed in this example is 0.28-0.35%.

[0047] Experimental Example

[0048] The same batch of fresh leaves (variety Longjing 43) was treated by light cycle combined with addition of exogenous enzymes to process black tea, and the same wilting, rolling, fermentation and drying processes were used. The TF content of the black tea processed by different exogenous enzymes and enzyme combination is shown in the following table:

[0049] Unit: %

[0050]

[0051] From the above table, it can be seen that, compared with the processing of black tea by different exogenous enzymes and enzyme combination, tannin enzyme can significantly increase the content of tea yellow, and the combination of pectinase and tannin enzyme has the best treatment effect.

[0052] Comparative Example

[0053] 1) Fresh leaf picking: Longjing 43 variety was selected, and the picking time was in June, and the picking tenderness was one bud and two leaves (EC content 2.0%, EGC content 3.5%, total catechin content 17.5%);

[0054] 2) Wilt: natural wilt, spread on the wilt frame, and the wilt degree was that the wilted leaf moisture content reached 62-64%.

[0055] 3) Rolling: the rolling machine is used for rolling, the rolling time is 50-70 min, the pressure mode is "light-heavy-light", wherein the light pressure time is 5-10 min, the heavy pressure time is 40-50 min, and the last light pressure time is 5-15 min.

[0056] 4) Deblocking: the rolled leaves are deblocked by a deblocking machine;

[0057] 5) Fermentation: the low-temperature fermentation mode is adopted, the fermentation temperature is 30°C, and the fermentation time is 4-5 hours.

[0058] 6) Drying: the two-step drying method of rough fire and full fire is adopted, the rough fire temperature is 110-130°C, the time is 8-15 min, the full fire temperature is 60-80°C, and the time is 60-90 min.

[0059] The black tea sample TF content processed in the example is 0.10-0.20%.

Claims

1. A method for preparing high TF content black tea by combining cyclic light curing with exogenous complex enzyme catalytic oxidation, characterized in that The method comprises the following steps: 1) picking fresh leaves: picking tea tree fresh leaves with certain tenderness; 2) circulating light withering: adopting white light and dark alternation withering; the specific steps of circulating light withering are as follows: thin spreading tea fresh leaves on a withering machine, the spreading thickness is 2-4 cm, the withering machine is a multi-layer structure, the uppermost layer is a light layer, white light source is supplemented, the light intensity is 2000-3000 Lx, the withering machine moves along with the track to realize the circulation of the upper and lower tea leaves, light and dark circulation, the ratio of light time to dark time is 1:3-1:5, the light and dark alternation times are 3-5 times; 3) adding enzyme: uniformly spraying a compound enzyme solution composed of tannin enzyme and pectinase on the withered leaves; wherein the tannin enzyme is prepared by Aspergillus niger fermentation, the enzyme activity unit is 1000 U / g, the enzyme activity unit of pectinase is 1000 U / g, and the mass ratio of tannin enzyme to pectinase is 1:1-3:1; 4) green leaf rolling: rolling the withered leaves by a rolling machine; 5) rolling: rolling by a rolling machine, the rolling environment temperature is 32-36℃, and the rolling time is 50-70 min; 6) de-blocking: de-blocking the rolled leaves by a de-blocking machine; 7) low-temperature fermentation: placing the tea leaves in a fermentation room or a fermentation machine for low-temperature fermentation, the fermentation temperature is 15-20℃, and the fermentation time is 2-3 hours; 8) drying: adopting two-step drying method of light fire and sufficient fire for drying treatment.

2. The method for preparing high TF content black tea by combined exogenous complex enzyme oxidation with cyclic light curing and withering according to claim 1, characterized in that The tenderness of the fresh leaves picked in step 1) is one bud and two leaves, the picking time is May to July, and the variety needs to meet the content requirements of part of catechin composition, that is, the EC content is higher than 2.0%, the EGC content is higher than 3.0%, and the total catechin content is higher than 15.0%.

3. The method for preparing high TF content black tea by combined exogenous complex enzyme oxidation with cyclic light curing and withering according to claim 1, characterized in that The mass ratio of the compound enzyme to the tea fresh leaves in step 3) is 1:500-1:1000, the compound enzyme treatment method is first fully dissolved with pure water, the solid-liquid ratio is 1:5-1:20, after dissolution, the supernatant is uniformly sprayed on the tea leaves in the form of mist droplets by centrifugation at 5000 r / min for 10 min.

4. The method for preparing high TF content black tea by combined process of cyclic light curing withering and exogenous complex enzyme oxidation according to claim 1, characterized in that The specific way of green leaf rolling in step 4) is as follows: placing the enzyme-added tea leaves in a rolling machine, setting the rotating speed to 15-30 r / min, and rolling for 60-90 min.

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