What is the withering of tea​

Explanation:

Plucking the leaf initiates the withering stage, in which the leaf becomes flaccid and loses water until, from a fresh moisture content of 70 to 80 percent by weight, it arrives at a withered content of 55 to 70 percent, depending upon the type of processing.

After tea leaves are picked, they are put on racks for withering, during which warm, dry air removes much of their moisture. The leaves are then rolled to break up the cells to hasten fermentation. The rolled leaves are broken up and—except for those used for green tea—taken to fermenting rooms until they turn a bright yellow. Drying with hot air stops the fermentation. Grading is done by sieves to separate large from small and broken from unbroken leaves. Finally the tea is packed into moisture-proof plywood cases, lined with aluminum.

In the traditional process, fresh leaf is spread by hand in thin layers onto trays or sections of coarse fabric called tats. It is then allowed to wither for 18 to 20 hours, depending upon several factors that include the temperature and humidity of the air and the size and moisture content of the leaf. Withering in the open air has been replaced by various mechanized systems. In trough withering, air is forced through a thick layer of leaf on a mesh in a trough. In drum withering, rotating, perforated drums are used instead of troughs, and in tunnel withering, leaf is spread on tats carried by mobile trolleys and is subjected to hot-air blasts in a tunnel. Continuous withering machines move the leaf on conveyor belts and subject it to hot air in an enclosed chamber, discharging withered leaf while fresh leaf is simultaneously loaded.

Mechanized systems greatly reduce withering time, but they can also lower the quality of the final product by reducing the time for chemical withering, during which proteins and carbohydrates break down into simpler amino acids and sugars, and the concentration of caffeine and polyphenols increases.

the underline word is basically like a prepositional phrase.

wallop

to hot or strike with a hand blow

explanation: