Comparative analysis of polyphenol content and antioxidant capacity in three onion types:

In this study, three onion types (white, red, and Welsh onions) were examined to determine the differences in their polyphenol contents and antioxidant capacities (hydrophilic oxygen radical absorbance capacities: H-ORAC value) across different parts and assess the effects of storage and cooking on these properties. Polyphenol content and antioxidant capacity varied by the raw onion part, with the highest values observed in the peel, followed by the leaves and core. Notably, polyphenol contents of the tested onion species increased with storage. Properties of polyphenol content and antioxidant capacity were impacted by the cooking method, with boiling reducing, whereas stir-frying significantly increasing the onion polyphenol content and antioxidant capacity. A significant positive correlation between polyphenol content and antioxidant capacity was observed in the powdered onion samples analyzed in this study.