Multi-radical (ORAC MR5 ) antioxidant capacity of selected berries and effects of food processing

BACKGROUND: Fruits and berries are known to contain relatively high amounts of antioxidant/bioactive compounds. Several methods have been used for measurement of antioxidant capacity (AC), but not all methods have direct relevance to in vivo antioxidant status. OBJECTIVE: Determine AC in berry/fruit samples, processed berry products, and purified compounds by utilizing 5 different biologically relevant free radical/oxidant sources. METHODS: Samples were assayed for AC capacity using 5 different free radical/oxidant sources: peroxyl radical (ORAC), hydroxyl radical (HORAC), peroxynitrite (NORAC), superoxide anion (SORAC) and singlet oxygen (SOAC)]. Total AC (sum of AC with 5 individual radicals) was expressed as Oxygen Radical Absorption Capacity using Multiple Radicals (ORAC MR5 ). RESULTS: SOAC contributed more than 60% of ORAC MR5 in blackberries, sweet and tart cherries; and no detectable levels of SOAC were found in strawberries, black currants and raspberries. Whole fruit purees of mango, wild blueberry and cherry contained 95, 85 and 67% respectively of total ORAC MR5 from SOAC. However, freeze dried wild blueberry powder from same production season had only 28% as SOAC and 42 and 22% as ORAC and HORAC. Blueberry/Pomegranate and Mango/Pineapple smoothies had 67% and 77% of ORAC MR5 as SOAC. CONCLUSIONS: The antioxidant quenching potential using 5 different radical/oxidant sources of different berries and fruits varied widely and understanding this variation may be helpful in understanding health benefits of different berries and foods.