The Importance of Withering in Tea Processing

Withering is an important process in tea production that involves reducing the moisture content of tea leaves to prepare them for further processing. Once tea leaves are harvested, they start to wilt naturally, and tea producers control the withering process to ensure that it occurs evenly. The withering process is crucial to the development of aroma and flavor compounds in tea leaves. The process involves closely monitoring humidity, temperature, and airflow to ensure the leaves lose a desired percentage of water content.

During withering, the moisture content in the tea leaves is reduced by about one-third to one-half, making the leaves flaccid and pliable. This softens the leaves and prepares them for further processing, including shaping and rolling. Chlorophyll in the leaves begins to degrade, caffeine levels slowly rise, and flavor and aroma volatiles develop in the leaves while grassy aromas dissipate.

Tea producers must closely monitor the withering process to ensure that the leaves wither evenly. The process is complete once the tea leaves have achieved a desired percentage of water loss, determined by the final weight of the leaves or the flaccidity and changes in the aroma of the leaves. A controlled wither can occur outdoors with tea leaves laid out gently on bamboo mats or tarps or indoors in troughs with forced air. If necessary, the air may be heated to speed up the process.

The withering time can also be used to store the fresh leaves before subsequent processing. During “chemical withering,” the leaves are not aerated on an ongoing basis but are subjected to cool air from time to time. No chemicals are added to the leaves in this process. Instead, the word “chemical” refers to the natural chemical changes that occur in the leaves. The caffeine content increases during this process, particularly in the case of black tea. The more effective the withering process, the more invigorating the finished tea product.

New flavors and aromas develop over time as many of the chemical compounds in the leaves disintegrate into volatile compounds during the withering process. Skilled tea producers can tell when the withering process is complete not only by the weight of the leaves but also by their sense of smell. Withering plays a crucial role in tea production, particularly in black tea, but also impacts the flavor and aroma of other types of tea.