Results and discussion
Total phenolic content of GTPs
To evaluate polyphenol content in GTPs, Folin & Ciocalteu test is used, results are displayedin Fig. 1. The most important
total phenolic content in GTPs was found in the fraction 100–
180 μm at 6000 rpm, 328 mg GAE/100 g DM. Values of TPC
increased when granulometry decreased from 500 μm to
50 μm. However, between 20 μmand 50 μm, TPCs decreased
dramatically to 192 mg GAE/100 gDM(6000 rpm). The nonground
tea extract showed a high TPC, 305 mg GAE/100 g
DM, which is superior than every GTPs obtained at 18,
000 rpm. This can be explained by the speed increase from
6000 rpm to 18,000 rpm which leads to a temperature rise
causing a loss of catechin content, as reported by Chen et al.
(2001). Optimal parameters to obtain the highest TPC were
the 100–180 μm sieve at 6000 rpm. The use of a faster grinding
speed led to lower TPC values.