Twinings of London Green Tea, 2 Oz, Carton Of 25 - Unlike black tea, green tea leaves are not oxidized at all. To prevent tea from oxidizing, the freshly-picked leaves are either pan-fried or steamed prior to rolling. This process stops the enzymatic activity in the leaf, allowing the leaves to retain their green colour and provide a lighter tasting tea. Green tea is mostly produced in China, where 80% of the world's green tea is sourced.