Effect of superfine grinding on quality and antioxidant property of fine green tea powders

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 center dot OH and O-2(-) 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 water-soluble 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 center dot OH. Based on the above analysis, it suggested that superfine grinding time should be controlled within 30-50 min, with ideal parameters of GTP: X: 4.93-4.75%, d(50): 20.3-13.5 mu m, rho(bulk): 0.323-0.297 kg/m(3), rho(tapped): 0.666-0.614 kg/m(3). 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. (C) 2011 Elsevier Ltd. All rights reserved.