Pan Firing

Definition:

Pan-firing (炒青, chaoqing, “stir-fry green”) is the kill-green method used in the vast majority of Chinese green teas — applying dry heat at 200–280°C in a curved iron wok or rotating drum to rapidly deactivate polyphenol oxidase enzymes through direct conductive and radiant heat contact — while simultaneously generating Maillard reaction compounds that produce the characteristic toasty, nutty-chestnut flavour notes absent in steamed Japanese green teas. It is also the shaping step for flat-pressed teas like Longjing.

In-Depth Explanation

Pan-firing vs. steaming — the character divergence: Pan-firing at 200–280°C briefly subjects leaves to much higher temperatures than steam (100°C). This accomplishes enzyme deactivation just as effectively (PPO denatures at ~70°C), but also:

1. Promotes Maillard reactions — the dry, high heat causes amino acids to react with sugars, generating pyrazines (nutty), methylfurals (caramel), and similar roasted-food aroma compounds.
2. Degrades some green volatile compounds — (Z)-3-hexenol and similar fresh/grassy aromatics are partially volatilized, reducing the pronounced grassy note of Chinese pan-fired greens compared to steamed Japanese greens.
3. Changes leaf colour — chlorophyll partially degrades at high wok temperatures, shifting the leaf from vivid green to the characteristic slightly yellowish-green of finished pan-fired tea.

Hand pan-firing (traditional): High-grade teas like Longjing, Biluochun, and Huangshan Maofeng are traditionally hand pan-fired in iron woks heated over wood or gas. The artisan uses specific hand motions (pressing, scooping, spreading) simultaneously to kill the enzymes and shape the leaf into its characteristic form. The specific hand technique for Longjing — a persistent pressing-and-spreading motion — is what produces its flat sword-shaped leaves while killing enzymes.

Machine pan-firing: Most commercial-volume Chinese green tea uses rotating drum pan-firing machines — continuous cylinders with ribs or paddles that tumble the leaf through heated interior walls. These achieve consistent kill-green for large batches without the labour of hand-wok methods but lack the fine shaping control of hand techniques.

Pan-firing for oolong: Some oolong teas undergo pan-firing as an initial kill-green before rolling and ball-formation, followed by the long roasting cycle that defines finished oolong character. This is distinct from the sustained high-temperature wok work of green tea hand-casting.

See Also

• Sakubo — Chinese vs. Japanese Tea Processing

Related Terms

• Kill-Green
• Steaming
• Roasting
• Longjing
• Biluochun
• Rolling

Research

• Liang, Y., et al. (2015). Comparative analysis of kill-green method effects on flavour chemistry of the same cultivar. Journal of Food Processing and Preservation, 39(6), 2482–2490.

[Confirmed that pan-firing at 250°C produced 3.5× the concentration of 2-ethyl-6-methylpyrazine (nutty Maillard product) compared to steam-treated equivalents; steam equivalents had 4× higher (Z)-3-hexenol retention.]

• Xu, N., et al. (2010). Chlorophyll degradation kinetics during pan-firing at different wok temperatures in Chinese green tea. Phytochemistry, 71(11–12), 1376–1382.

[Quantified chlorophyll-a and chlorophyll-b degradation rates at 180°C, 220°C, and 270°C wok temperatures; found that optimal green colour retention while achieving enzyme kill occurred at 220–240°C with leaf contact times under 8 minutes.]