Polyphenolic content and antioxidant capacity of white, green, black, and herbal teas: a kinetic study

Camellia sinensis teas, and tisanes derived from herbs or fruit, are rich in polyphenolic, antioxidant compounds. This study compared the total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), DPPH radical scavenging capacity, and caffeine content of teas (black, green, white, chamomile, and mixed berry/hibiscus) over a range of infusion times (0.5-10 mins) at 90C. Green, followed by black tea, respectively, had the greatest TPC (557.58 and 499.19g GAE/g), TFC (367.84 and 325.18g QE/g), FRAP (887.38 and 209.38g TE/g), and DPPH radical scavenging capacity (1233.03 and 866.39g AAE/g). Caffeine content per cup (200mL) in black, green, and white tea was 63, 51, and 49mg respectively. Changes in the phenolic content and antioxidant capacity of teas were modelled using zero, first, and fractional-conversion-first-order (FCFO) kinetic models. Results fitted a FCFO kinetic model, providing useful data for maximum phytochemical preservation in the optimisation of industrial and domestic processing. As a dietary comparison, green, black, and white tea were found to have a greater phenolic content and antioxidant capacity than fresh orange and apple juice. It can be concluded that green and black teas are significant sources of dietary phenolic antioxidants.