O2 and temperature were documented to exert obvious influence
on stability of catechins in green tea. The investigation by
Neilson et al. (2007) showed that O2 could promote catechin
degradation. Chen, Zhu, Tsang, and Huang (2001) reported that 20%
of catechin was lost, while being heated in water at 98 C for 7 h.
Superfine grinding increases superficial area of GTP, and as a result
the contact area with oxygen could be increased largely, which
leads to catechin oxidation. Meanwhile, heat could be produced
during superfine grinding process, and the longer superfine
grinding time is, the higher the mill cavity temperature is, which
also promotes oxidation of catechins and causes more loss