When we think of Tea, we are enveloped in a sense of greenness, freshness, and subtle fragrance. Born between heaven and earth, tea absorbs the essence of nature and the vitality of the sun and moon, evoking feelings of tranquility and simplicity. The essence of tea lies in its “youth,” from the picking of a single leaf to the processes of fixation and sun drying, culminating in the delicate aroma on our tongues. But how many different meanings does “youth” hold within the world of tea?

1

Fixation / The First Step in Becoming Tea

The fresh, grassy flavor is an inherent characteristic of natural plants, and it's unavoidable in tea. In the production process of Pu'er tea, fixation is used to remove this grassy taste through thermal chemical changes, evaporating moisture and allowing the grassy flavor to diminish, revealing the tea's aroma.

Fixation, as the term suggests, involves the “killing” of the “youth,” where “youth” refers to the fresh, green leaves. Fixation destroys the structure of these fresh leaves, and the process involves applying high temperatures to rapidly transform the internal components of the leaves. As we know, enzymes are substances found in tea, biological macromolecules with catalytic functions that act as biological catalysts. They can speed up or slow down biochemical reactions without altering their direction or products. Most enzymes are composed of proteins (with a few being RNA), and their activity is easily influenced by factors such as temperature and chemical environment (like pH).

Under high temperatures, the protein structures of enzymes undergo irreversible damage, completely losing their enzymatic activity. The fixation process in tea leverages this property of enzyme denaturation, effectively halting the activity of oxidizing enzymes in the fresh leaves.

The primary purpose of fixation is to quickly use high temperatures to destroy the activity of polyphenol oxidase in the fresh leaves, inhibiting the enzymatic oxidation of polyphenols. This allows the internal components to form the color, aroma, and taste characteristics of Pu'er tea through non-enzymatic processes. Fixation also removes some moisture, softening the leaves for rolling and shaping. Additionally, it eliminates the grassy smell of the fresh leaves, allowing the tea to release a captivating fragrance. In summary, the aim of fixation is to alter the structure and properties of the fresh leaves, laying a solid foundation for the unique qualities of the tea. This is both the purpose of fixation and the fundamental principle behind the technical measures employed.

2

Sun Drying / A Fundamental Rule for Pu'er Tea

After fixation and rolling, leaves that are dried in the sun are collectively referred to as “sun-dried rough tea.” Pu'er tea from Yunnan Province must be sun-dried. Sun drying, as the name implies, means drying the tea with sunlight. It refers to the method of drying the rough tea rather than the fixation process. The typical steps in making Pu'er tea are: plucking, spreading out, fixation, cooling, rolling, and drying. Sun drying follows the rolling step. The key difference between sun drying and other drying methods like pan firing and oven drying is “temperature.” Pan firing and oven drying involve higher temperatures that essentially terminate the life of enzymatic substances in the tea. However, sun drying uses natural sunlight with lower temperatures, preserving the potential for active substances to grow. Sun-dried tea has a loose shape, appears black, and has a distinctive sun-dried aroma that presents as a fresh, floral scent. After brewing, the aroma lingers, and the taste is pure. Sun drying also contributes to the potential for Pu'er tea to improve with age, creating a vitality for long-term storage.

It's important to note that “sun drying” doesn't necessarily mean “drying in the sun” all the time; during rainy or overcast days, drying in an oven or air-drying may be considered, but it must be done at low temperatures, which is the crucial point. Typically, temperatures should not exceed 60 degrees Celsius. Although sun drying takes longer, it preserves the original flavor and active substances of the tea. Maintaining appropriate low temperatures is a significant difference between Pu'er tea and Green Tea in terms of processing techniques. Green tea uses high-temperature fixation to quickly enhance its aroma, but it cannot achieve the improvement in flavor that Pu'er tea enjoys with age. Green tea must be consumed within a certain period; otherwise, the flavor will become thin and bland, losing its value. In contrast, Pu'er tea is a product of slowness and time, embodying the concept of “slow work yields fine results” in its production process.

3

Pan Firing and Oven Drying / A Variety of Fragrances Belonging Only to Green Tea

Pan firing and oven drying are part of the production process for green tea. Their purpose is the same: to stop the fermentation process using high temperatures. The difference lies in the method – one uses high-temperature pan firing, while the other involves direct high-temperature baking. Pan firing involves using a gentle fire in a Wok to wilt the tea leaves during the production process. Through manual rolling, the moisture in the leaves is rapidly evaporated, interrupting the fermentation process and preserving the essence of the tea juice.

Green tea that is dried after fixation and rolling is called oven-dried green tea. Oven drying involves high-temperature drying, resulting in teas with a strong fragrance. There have been instances where merchants mixed oven-dried green tea into Pu'er tea to enhance its aroma, but this is detrimental to the subsequent transformation of Pu'er tea, so consumers should be cautious when purchasing.

Oven-dried and pan-fired green teas cannot be used as raw materials for Pu'er tea and are unsuitable for processing into Pu'er tea. The aging and “fermentation” of Pu'er tea primarily rely on the automatic oxidation of the sun-dried rough tea, the enzymatic oxidation of polyphenols, and microbial action. Oven-dried and pan-fired rough teas undergo high-temperature fixation, which denatures and destroys polyphenol oxidase. Additionally, during the drying process, high temperatures are used for rapid drying, further destroying polyphenol oxidase. Oven-dried and pan-fired rough teas have low moisture content and cannot complete “natural aging,” making them unsuitable for processing into Pu'er tea.

4

Steam Fixation / The Highly Popular “Matcha”

Steam fixation is also part of the production process for green tea. Steam fixation is one of the earliest types of tea invented in ancient China. It uses steam to soften fresh tea leaves, followed by rolling and drying. Steam-fixed green teas are often characterized by their “three greens” – green in color, green in infusion, and green in leaves – which are visually appealing. Steam-fixed green tea is the primary type of green tea in Japan, and the tea used in Japanese tea ceremonies is the globally popular “matcha.”

5

Distinguishing Sun Drying, Pan Firing, and Oven Drying?

During fixation, sun-dried rough tea often uses wok fixation with lower temperatures, typically keeping leaf temperatures below 80°C. Fewer polyphenol oxidases are denatured, and low-boiling-point aromatic compounds do not completely disappear, resulting in a grassy aroma in the fixed leaves. The fixation is relatively tender. For oven-dried and pan-fired rough teas, various methods such as wok fixation, drum fixation, steam fixation, and hot air fixation can be used. These methods employ higher temperatures, typically keeping leaf temperatures above 90°C. Polyphenol oxidase is thoroughly destroyed, and low-boiling-point aromatic compounds vanish, leaving the fixed leaves with a clear fragrance and no grassy aroma. The fixation is relatively robust. Sun-dried rough tea uses lower temperatures for fixation, preserving enzymatic activity and retaining a grassy aroma, which is beneficial for the “fermentation” of Pu'er tea in later stages. Oven-dried and pan-fired rough teas use higher temperatures for fixation, thoroughly destroying enzymatic activity, which is detrimental to the “fermentation” of Pu'er tea in later stages.

In terms of taste, Pu'er tea made from sun-dried raw materials prioritizes bitterness and astringency, with a yellowish infusion color. Over time, the bitterness and astringency dissipate. Oven-dried and pan-fired teas have a refreshing taste, a greenish infusion color, and a slight aroma reminiscent of glutinous rice or chestnuts. However, they become bitter instead of sweet after aging. After many years of storage