Effects of tea processing on antioxidant agents in green tea = อิทธิพลของกระบวนการผลิตชาที่มีต่อสารต้านอนุมูลอิสระในชาเขียว


กฤษฏา โกวิทยะวงศ์


วิทยานิพนธ์. (2005) 79 หน้า



Fresh tea leaves contains high amount of polyphenols but more than 50 percent of these antioxidants are destroyed during processing. Therefore, effects of processing conditions on the antioxidant yield, especially, ECGC need to be investigated in order to determined the suitable processing condition for green tea processing with minimum EGCG loss. The results showed that the maximum loss of total polyphenols and tannin content occurred in panning and drying step. Polyphenols were degraded by thermo- physiochemical and oxidation reaction of enzymatic. Panning steps reduced total polyphenols and tannin around 10-15 percent on dry basis. Caffeine is more stable with only 2-3 percent reduction in every step while loss of chlorophyll loss in withering step by enzyme chlorollase was around 0.5-0.7 percent on dry basis. The tea product contained 1-3 percent moisture which was less than the standard (7 percent on dry basis). Therefore, the moisture content of tea in drying step could be increased to 7 percent by reducing the operating time. Moreover, overdrying tea product also results in unnecessary loss of total polyphenols