Tie Guan Yin- Sweet & Delicious Aftertaste Tie Guan Yin, also known as Oolong tea, semi-fermented tea, is one of the famous tea in China produced with excellent quality through the fixing, withering, rocking green, semi-fermented, baked and other processes. It contains a lot of nutrient compositions, such as: Tea Polyphenols, Catechin, Plant Alkalo..