Loose Leaf Tea

All green teas consumed for health reasons must be in the form of loose leaves, and the leaves must be mechanically damaged before drying. The scientific reasoning is as follows.

In a natural tea leaf (see illustration for Fresh unprocessed tea leaf), the tea catechins, like the EGCG molecules, are stored in small vesicles formed by membranes in the spongy mesophyll. These vesicle membranes must be broken for the antioxidants to be extracted into the hot water during tea brewing. In a properly processed tea leaf (see illustration for Properly processed tea leaf), the membranes of the vesicles in the mesophyll are broken, but the two surface epidermis layers are still intact so that the antioxidants released from or still in the broken vesicles are not squeezed out onto the surface of the dried tea leaves, as in a poorly preserved tea leaf, where the antioxidants on the tea leaf surface would easily be oxidized (see illustration for Poorly processed tea leaf). The experienced tea workers in the Chinese tea industry refer to this technical blunder as “losing the tea juice”.