Black tea is the most produced, consumed, and traded type of tea, with its unique flavor characteristics loved by consumers around the world, gradually becoming an indispensable part of daily life for numerous tea drinkers.
Black tea is also a significant component of China's six major tea categories. In 2019, China's black tea production reached 307,200 tons, up 17.29% year-on-year, accounting for 11% of total tea production.
Withering
Withering is the first step in black Tea processing, which involves thinly spreading fresh leaves to lose some of their water content. This process is closely related to subsequent tea-making steps and tea quality. During withering, a series of metabolic changes occur, laying the foundation for the formation of black tea's quality characteristics.
How can improvements in processing technology effectively enhance black tea quality? Researchers supplemented different types of light (ultraviolet, yellow, blue, orange, white (control), purple, green, and cyan) during withering and found that different light qualities significantly affect black tea quality.
Sensory Evaluation Results
The impact of different light qualities on the aroma and taste of black tea was particularly noticeable. Yellow, red, and orange light-treated black teas had a high and lasting sweet fragrance and a fresh, mellow taste, making them of the highest quality. Next were blue, ultraviolet, purple, and cyan light treatments, all of which were significantly better than no light or control treatments. Green light treatment was unfavorable for black tea quality, imparting a grassy odor.
Quality Component Analysis Results
Yellow, red, and orange light-treated black teas had significantly higher amino acid, Theaflavin, and Catechin contents compared to the control, with soluble sugar contents also showing varying degrees of increase. The content of polyphenols did not differ significantly from the control, contributing to a fresher, richer taste profile. Green light treatment led to a significant decrease in amino acid content compared to the control, with no significant differences observed in soluble sugars and polyphenols.
Main References (Sources):
Zhang Beibei. The Effect of Different Light Qualities on the Quality of Black Tea [D]. Huazhong Agricultural University, 2013.
The cited literature is not fully referenced, and images are mainly sourced from the internet.
Reproduction of all content for profit without permission is prohibited. For reprints, etc., please leave a message in the background or indicate the source.
Withering Time and Standards for Black Tea
The withering time for black tea is 4 to 8 hours, with the moisture content of withered leaves ideally at 60 to 64%. Appropriately withered leaves will be wrinkled, soft in texture, and pliable. Fresh leaves become limp and soft, easily bent without breaking. When squeezed, the leaves feel soft and can be tightly balled; when released, they slowly loosen. The glossy appearance of the leaves disappears, turning dark green, with the grassy scent diminished and replaced by a fragrant aroma.
China's black tea is divided into three categories: congou black tea, broken black tea, and lapsang souchong. Although the production methods vary slightly, they all include withering, Rolling, fermentation, and Drying.
The formation of color, aroma, and taste is a similar chemical change process, with only slight differences in conditions and degree.
Withering is the first step in black tea production, where the fresh leaves undergo a period of dehydration, transforming from firm and brittle to wilted and drooping.
After withering, the moisture evaporates appropriately, making the leaves softer and more flexible, facilitating shaping. Additionally, during this process, the grassy smell dissipates, revealing the tea's fragrance, a critical stage for the development of black tea's aroma.
Methods of withering: natural withering indoors, withering in troughs, withering using machines, and various forms of heated withering. Currently, the main methods used are withering in troughs or natural withering indoors.
This process typically starts in the evening and continues until early morning. The withering time is generally between 4 and 8 hours, depending on the age and tenderness of the leaves. Suitable temperature, humidity, and air circulation are required during withering.
The duration of withering depends on the harvest time, season, weather, and the freshness of the leaves. Mastery of timing requires long-term experience.
During this process, tea makers must observe the changes in the fresh leaves every half hour or so and toss them to ensure even heat distribution. The tea makers must focus carefully on the changes in the fresh leaves.
If they are not vigilant and delay tossing the leaves, they can quickly become over-wilted or scorched, rendering the entire batch unusable and causing significant economic losses. There is a specific technique for tossing the leaves, requiring consistent force and area coverage, testing the patience and attention to detail of the tea makers.
Three Methods of Withering
1. Natural withering – Fresh leaves are evenly spread on bamboo curtains or screens and placed in a well-ventilated, cool, and dry area.
2. Sunlight withering – Fresh leaves are evenly spread and withered under direct sunlight.
3. Trough withering – Fresh leaves are evenly spread on a withering trough and withered.
Effects of Insufficient and Excessive Withering
Insufficient withering results in hard and brittle leaves, which break easily during rolling, producing thin and watery tea juice. If rolling is insufficient, fermentation will be uneven and difficult to achieve the desired level. If rolled thoroughly, the tea will break into small pieces, resulting in short, sticky clumps. The finished tea will have a short, broken shape with many fragments, low aroma, and weak flavor, with a mixed leaf base and strong grassy taste.
Excessive withering causes the buds and tips to become dry and brittle, the leaves to become dry and hard, and the tea juice difficult to extract. The tea strands will not be tight, fermentation uneven, and the finished tea will be loose and pale, with a light flavor and a dark, mixed leaf base.
Appropriately withered leaves will be wrinkled, soft in texture, and pliable. Fresh leaves become limp and soft, easily bent without breaking. When squeezed, the leaves feel soft and can be tightly balled; when released, they slowly loosen. The glossy appearance of the leaves disappears, turning dark green, with the grassy scent diminished and replaced by a fragrant aroma.