The influence of different water types and brewing durations on the colloidal properties of green tea infusion

Abstract

Green tea infusions were prepared with three different water types: distilled water, commercial mineral water and CaCl2 added distilled water (at 20mgL(-1)). The impact of different water type on the colloidal particle parameters, namely size, polydispersity index (PDI) and zeta potential, was examined within 24h. Our results indicate that distilled water green tea infusion (DWT) brewed at 80 degrees C for 5min contained the smallest particles (242.17 +/- 11.78nm) as examined by dynamic light scattering (DLS). Moreover, DWT showed smaller size increase during the 24h storage than that of mineral water tea and CaCl2 added water tea infusion. The morphology characteristics of green tea infusion particles were visualised by transmission electron microscope (TEM) which revealed that green tea infusion particles had heteromorphic shapes. Our results suggest that mineral composition of water impacts the colloidal size and stability of green tea infusion. Additionally, DLS and TEM could be useful tools to provide colloidal information which is important to understand quality characteristics of green tea infusion during processing and storage.