Effects of Roasting on Phenolic Composition and In vitro Antioxidant Capacity of Australian Grown Faba Beans (Vicia faba L.)

Faba bean phenolic compounds encompassed phenolic acids, flavonols, proanthocyanidins and anthocyanins. Roasting faba beans for 120 min decreased the total phenolic, flavonoid and proanthocyanidin contents by 42, 42 and 30 %, respectively. Roasting beans for 120 min decreased the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, total equivalent antioxidant capacity and ferric reducing antioxidant power by 48, 15 and 8 %, respectively. High performance liquid chromatography-post column derivatisation revealed the generation of new phenolic compounds as a result of roasting. Antioxidant mechanism of bean less-polar phenolic compounds was largely based on free radical scavenging activity. The bean phenolic compounds with reducing capability were heat stable. Roasted faba bean extracts (70 % acetone, v/v) were fractionated into relatively polar and non-polar fractions; the latter contributed the majority of the antioxidant capacity. The extracts from beans with different seed coat colours differed in their phenolic compositions, which suggest different levels of potential benefits to health. Although roasting initially lowers the bean antioxidant capacity, prolonged roasting at 150 °C for 60 min and longer causes generation of new phenolic compounds and an increased antioxidant capacity. The findings encourage a wider ultilisation of faba beans for human foods particularly in baked/roasted products.