Sha qing — heat fixation (殺青, shāqīng)

Sha qing (杀青), or heat fixation, reduces the activity of enzymes involved in tea-leaf oxidation. It is important in green and yellow tea, oolong and the raw material for pu-erh.

For green tea, fixation happens early to limit enzymatic oxidation. For oolong it follows partial oxidation. Leaves may be heated in a pan or drum, or steamed. Hand processing is not required, and the country of production alone does not identify the method.

Fixation, final drying and roasting have different purposes, although some processes combine operations. Rolling, shaping and drying may still follow fixation. Heat changes aroma, moisture and leaf properties as well as enzyme activity.

Pu-erh ageing cannot be explained solely by “surviving enzymes”: storage involves various chemical and microbial processes. A cup may reveal burnt or coarse grassy notes, but cannot tell you the exact fixation conditions. The term also does not mean sterile or contaminant-free tea.

Related teas

Chinese tea glossary