تعيين المحتوى الكلي لمتعددات الفينول وللفلافونويدات والكاتشين EGCG-(-) في منقوع خمسة انواع من الشاي المحضر بطريقة النقع المستمر

Total polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin gallate ((-)-EGCG) were determined in five commercial tea infusions by continuous infusion method, using the ratio 20g of tea to 1L of water at 85±5 °C and brewing time between 5-180 min. The results showed that the highest content of TP was measured after 180 min of brewing for the three white teas (Wt-S, Wt-P and Wt-A), while it took a shorter infusion time for the black and the green tea (5 and 30 min, respectively). The results also indicated that TP concentration reached a similar value for all studied teas after brewing for 60 min. The highest amount of EGCG was obtained after 5 min of brewing for green tea, and 180 min for Wt-S. Whereas black tea infusion had the lowest amount of EGCG at all brewing times. TP and EGCG content in tea infusions differ according to several factors, such as tea type, form and infusion time. However it's advised to brew for one hour at most when preparing tea infusion by continuous method to release the highest amount of TP and EGCG. Any further time might cause a loss of some important compounds in tea, as well as wasting time and energy