The production of White Tea is the simplest among the six major types of Tea, consisting only of wilting and drying. Wilt is the first step in processing white tea and also the most important one. However, many people have a vague understanding of the term “wilt.” So what exactly is “wilt”?
Let's look at how “wilt” is defined in the “Chinese Tea Science Dictionary.”
The process of removing part of the moisture from fresh leaves and promoting changes in their internal chemical components. It is the first step in making white tea, Black Tea, and Oolong Tea. After losing a certain amount of water, the leaves become soft, respiration accelerates, generating heat. The permeability of leaf cell membranes increases, and enzyme activity is enhanced, causing the following series of biochemical changes:
Protein hydrolysis, increasing amino acids; reduction in starches and disaccharides, increase in monosaccharides; decrease in protopectin, increase in water-soluble pectin; some tea polyphenols combine with proteins, some are oxidized, and there is a reduction in water-soluble tea polyphenols; destruction of chlorophyll; Vitamin C is oxidized and decomposes under the action of ascorbate oxidase; increases in water-soluble organic acids such as oxalic acid, succinic acid, citric acid, and inorganic acids like phosphoric acid, raising the acidity of leaf cell sap; an increase in aromatic substances, especially nerol, linalool oxide, (E)-2-hexenal, phenethyl aldehyde, and a significant increase in carbonyl compounds, giving the wilted leaves aroma.
So is wilting just about placing the tea leaves on bamboo trays to air dry, allowing them to lose water naturally? It's not that simple.
In fact, white tea is the type of tea that is most particular about the method of wilting. The wilting of white tea is not simply the loss of water from the fresh leaves, but rather, under certain external temperature and humidity conditions, as water gradually evaporates, the concentration of leaf cells and the permeability of cell membranes change, and various enzymes are activated. Changes in substances such as tea polyphenols, amino acids, sugars, caffeine, and chlorophyll form the unique flavor and quality characteristics of white tea.
# What Factors Affect the Wilt of White Tea?
The factors affecting the quality of white tea wilt include: “temperature, humidity, ventilation,” as well as the duration of wilting and the thickness of the spread leaves.
I. Temperature and Humidity
Temperature and humidity are necessary conditions for promoting biochemical reactions and are important environmental factors affecting the effect of wilting. In a high-temperature wilting environment, the leaf temperature is also high, and the relative speed of water movement accelerates, making it easier to lose water. At the same time, the relative humidity of the wilting environment decreases as the wilting temperature rises, meaning that higher temperatures result in lower relative humidity, and the rate of water loss during white tea wilting is faster. Conversely, the rate of water loss slows down.
If the rate of water loss is too fast or too slow, it will affect the quality of white tea to varying degrees. Rapid water loss leads to shorter wilting times, which can prevent normal completion of the physicochemical changes during wilting and cause uneven wilting effects.
Excessively high temperatures can lead to intense oxidation and condensation reactions of polyphenols, turning the tea red, while excessively low temperatures and humidity can cause long wilting times leading to mold growth.
So is wilting just about placing the tea leaves on bamboo trays to air dry, allowing them to lose water naturally? It's not that simple.
In fact, white tea is the type of tea that is most particular about the method of wilting. The wilting of white tea is not simply the loss of water from the fresh leaves, but rather, under certain external temperature and humidity conditions, as water gradually evaporates, the concentration of leaf cells and the permeability of cell membranes change, and various enzymes are activated. Changes in substances such as tea polyphenols, amino acids, sugars, caffeine, and chlorophyll form the unique flavor and quality characteristics of white tea.
# What Factors Affect the Wilt of White Tea?
The factors affecting the quality of white tea wilt include: “temperature, humidity, ventilation,” as well as the duration of wilting and the thickness of the spread leaves.
I. Temperature and Humidity
Temperature and humidity are necessary conditions for promoting biochemical reactions and are important environmental factors affecting the effect of wilting. In a high-temperature wilting environment, the leaf temperature is also high, and the relative speed of water movement accelerates, making it easier to lose water. At the same time, the relative humidity of the wilting environment decreases as the wilting temperature rises, meaning that higher temperatures result in lower relative humidity, and the rate of water loss during white tea wilting is faster. Conversely, the rate of water loss slows down.
If the rate of water loss is too fast or too slow, it will affect the quality of white tea to varying degrees. Rapid water loss leads to shorter wilting times, which can prevent normal completion of the physicochemical changes during wilting and cause uneven wilting effects.
Excessively high temperatures can lead to intense oxidation and condensation reactions of polyphenols, turning the tea red, while excessively low temperatures and humidity can cause long wilting times leading to mold growth.
△ Photograph by Chen Xinghua
III. Duration of Wilt
Under specified temperature and humidity conditions, the length of the wilting period has a direct relationship with the formation of quality. If too short, oxidation is insufficient, polyphenols content is high, resulting in a bitter and astringent taste. If too long, the main biochemical components are significantly consumed, leading to a bland taste, which is not conducive to the formation of quality.
The duration of wilting is related to the tenderness of the fresh leaves, climate, and season. From a climatic perspective, hot, humid, low-pressure weather (i.e., southern wind days) requires longer wilting times, while cool, dry northern weather allows for shorter wilting times. From the perspective of tenderness and season, spring tea has good tenderness, thick leaves, and high water content in the fresh leaves, requiring longer wilting times, while autumn tea has lower tenderness, thin leaves, and lower water content, allowing for relatively shorter wilting periods.
△ Photograph by Chen Xinghua
IV. Uniformity and Thickness of Spread Leaves
In the early stages of wilting, uneven distribution and excessive thickness of the spread leaves can lead to a lack of freshness and fullness in the taste of white tea and a mottled coloration of the leaf base.
In summary, the evaporation of moisture from fresh leaves during white tea wilting interacts with the environment. The temperature of the leaf layer directly affects the condition of water evaporation from the fresh leaves. The loss of water from the fresh leaves is influenced by the combined effects of the relative humidity of the leaf layer, the temperature of the leaf layer, and ventilation conditions. Therefore, white tea appears simple, yet it is truly full of subtleties and profundities.
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