The low temperature and high humidity environment of the spring Tea season in Guizhou, along with the performance differences in processing equipment, affect the quality of Spring Tea processing. To improve the quality of spring tea products and highlight the regional characteristics of Guizhou Green Tea, mastering key techniques such as withering, Fixation, shaping, and drying is essential. The following provides an explanation based on the critical common technologies in green tea processing:
Program-controlled withered leaves in the withering room
I. Withering
Withering is the first process in green tea processing. Good withering can improve the efficiency of fixation and better address issues with bitterness and astringency in the tea liquor.
1. Issues
(1) Thicker layers of withering leaves often require turning to ensure uniform withering, which can cause mechanical damage to the leaves.
(2) Withering equipment lacks auxiliary heating devices, making it difficult to control the progress of withering.
(3) During withering, the digital display temperature of the auxiliary heating device is used as a reference, while ignoring the temperature of the withering leaves.
(4) The degree of withering is typically judged by the softness of the leaves and their color, neglecting the presence of stems.
Program-controlled unit for single-machine withering-drying dual-use equipment
2. Solutions
(1) Avoid turning or other operations that may cause mechanical damage during withering. The amount of withering leaves per square meter should be 1 to 3 pounds, and the blower of the withering equipment should be able to pass through the layer of leaves.
(2) Install auxiliary heating devices, and the leaf temperature during the hot air stage of withering should not exceed 28°C. Use intermittent hot air action combined with static withering. The leaf temperature during the hot air stage should not exceed 28°C, and the temperature during the static stage should be ambient temperature.
(3) The degree of withering should be judged based on the uniform loss of Water from buds, bud-leaves, or stem-leaves, supplemented by visual and olfactory features such as color and aroma.
Demonstration guidance for dynamic-static operation control points in trough withering
II. Fixation (Killing the Green)
The ultimate purpose of fixation is to inactivate enzymes, taking into account dehydration and shaping. Guided by the shape desired (straight, flat, curled, or granular), different fixation methods are used to achieve efficient fixation production.
1. Issues
(1) Unclear use of dehumidification in drum fixation machines.
(2) Insufficient solidification effect after strip fixation.
(3) Steam fixation results in a prominent water-stewed flavor due to excessive steam.
(4) Due to uneven thickness of the leaf layer, local scorching occurs during steam heat fixation, affecting subsequent processing.
(5) Immediate cooling of fixed leaves is neglected.
(6) Long-term stacking and rehumidification after over-fixation lead to quality deterioration.
2. Solutions
(1) Adjust the use of dehumidification devices during fixation based on the fixation effect. If the fixation is insufficient, dehumidification should be stopped to utilize moist steam for smothering fixation, achieving supplementary fixation. Conversely, if the fixation effect is good, reduce the duration of moist steam to avoid insufficient dispersion of moist heat and green odor.
(2) Strip fixation usually involves shaping. After strip fixation, adjust parameters such as temperature and equipment tilt angle based on equipment performance, extending the stir-frying time to achieve the desired shape.
(3) Adjust the steam volume to meet fixation needs while avoiding excessive steam leading to moist heat effects.
(4) Control the uniformity and thickness of the withering leaves.
(5) Fixed leaves should be cooled immediately to prevent stacking. Cooling and sifting equipment can be used in this step to achieve cooling and sifting effects.
(6) Avoid long-term stacking and rehumidification after over-fixation, which can cause quality deterioration.
Adjust the method and quantity of leaf feeding according to the performance of different fixation equipment
III. Rolling
Rolling is the process for shaping the product. Based on the consensus of alternating between light and heavy pressure, frequency-adjustable speed control and modular temperature control are key to improving rolling efficiency.
1. Issues
(1) Excessive or insufficient pressure, or too fast a rotation speed, leads to poor shaping effect or even damages the integrity of buds and leaves.
(2) Excessively long rolling time or prolonged stacking after rolling results in dark green leaves with a prominent green-stewed flavor.
2. Solutions
(1) The rolling time of fixed leaves in the initial rolling stage should not be too long, typically 15 to 30 minutes. This stage aims primarily to soften the veins (stems) and refine the strips, so rolling and rotation speeds should not be too fast, recommended at 20 to 30 rotations per minute. In the later stages of rolling, as the cells of the leaves break down, low-boiling-point odor substances and tea juice overflow, prolonged rolling can easily lead to a decline in tea aroma and taste quality. Frequency-adjustable rolling machines can achieve speed control.
(2) Re-rolling stage (if necessary). After the initial rolling leaves undergo dehydration treatment (or initial drying), further shaping is carried out. The rolling time is 12 to 15 minutes, and the duration of heavy pressure should not exceed 5 minutes.
(3) Proceed to the next process soon after rolling to avoid stacking.
(4) Modular temperature and humidity control during rolling is necessary.
Adjust pressure based on the movement state of rolling leaves
IV. Drying
The purpose of drying is to solidify the shape and develop aroma and taste qualities. Drying typically consists of initial drying and final drying (aroma enhancement). Drying is carried out based on the quality characteristics of the tea, such as preserving aroma and protecting color, requiring differentiated drying methods.
1. Issues
(1) During stir-frying and drying, prolonged exposure to high temperatures causes the product to exhibit a high-fire aroma.
(2) Excessively long stir-frying times result in more broken leaves (especially during the process of removing downy hair from emerald buds), a yellowish color, and insufficient luster.
(3) Insufficient drying time means that unpleasant odors like green smell are not thoroughly removed.
(4) The concept of interval drying is lacking, with most practices involving one-time drying consisting of initial drying plus final drying.
(5) Dust and fragments are not sifted out before drying, leading to high-fire and scorched flavors under subsequent temperature action.
2. Solutions
(1) Adopt a temperature strategy starting high and then decreasing based on the moisture content of the leaves being processed. For leaves with higher moisture content, high temperatures (110°C to 120°C) can be used for 12 to 20 minutes during initial drying. For leaves with lower moisture content, a temperature range of 60°C to 80°C can be used for 2 to 3 hours during final