Impact of Roasting to Total Phenolic, Flavonoid and Antioxidant Activities in Root, Bark and Leaf of Polyscias fruticosa

Abstract

Polyscias fruticosa belongs to Araliaceae family widely cultivated in Vietnam. It is a medical plant highly valued recently owing to its diversified therapeutic functions. It’s exploited in all parts including root, bark and leaf for medicinal purposes. In the herbal tea production, the final step is normally ended with the roasting in order to improve its flavor and aroma. There’s a concern about the detrimental effect of thermal roasting to the stability of phytochemical constituents. In this research, we attempted to evaluate the reduction of total phenolic (mg GAE/100 g), total flavonoid (mg QE/100 g), DPPH radical-scavenging ability (mM TE/100 g), FRAP ferric reducing antioxidant power assay (mM TE/100 g) in root, bark and leaf of Polyscias fruticosa under different roasting conditions. All samples were steamed in vapor for 30 seconds before being dried by convective dryer at 45°C for 6 hours to final moisture content around 12%. Then these samples would be roasted in different conditions (125/15; 130/12, 135/9, 140/6, 145/3, °C/minutes). Our results revealed that roasting at 135/9°C/minutes was appropriate to preserve the most phytochemical constituents.