Six Green tea powders (GTPs) were prepared from green tea with superfine grinding process. Their main
quality components were determined by chemical methods and the scavenging effects of GTPs on $OH
and O2.L in vitro were evaluated by using deoxyribose assay and xanthine oxidase method, respectively.
The results indicated that tea polyphenols and catechins contents decreased, while the contents of watersoluble
carbohydrates in GTPs increased markedly, and no significant difference in amino acids and
caffein with the decrease in particle size during superfine grinding, which benefited to reduce bitterness
and preserve briskness of GTPs. Meanwhile, superfine grinding increased extraction of TPS markedly,
which could lead to more potent scavenging capacity of GTPEs on $OH. Based on the above analysis, it
suggested that superfine grinding time should be controlled within 30e50 min, with ideal parameters of
GTP: X: 4.93e4.75%, d50: 20.3e13.5 mm, rbulk: 0.323e0.297 kg/m3, rtapped: 0.666e0.614 kg/m3. Under this
condition, we could prepare GTP with green and bright color, narrower and more uniform particle size
distribution, as well as possessing more food processing property.