Bioactive components, ABTS radical scavenging capacity and physical stability of orange, yellow and purple sweet potato ( I pomoea batatas ) powder processed by convection‐ or vacuum‐drying methods

Summary This study aims to investigate the antioxidant properties and physical stability of convection‐ or vacuum‐dried orange, yellow and purple sweet potato ( Ipomoea batatas ) powder upon room temperature storage at different relative humidity ( RH ) of 33%, 43%, 54% and 75% for 25 days. Both convection and vacuum‐dried samples had lower total phenolic content ( TPC ), anthocyanin content and antioxidant activity compared to the fresh samples. Vacuum‐dried powder retained higher antioxidant activity than convection‐dried powder. Storage of the powder at high RH of 75% resulted in apparent clump formation, which was likely attributed to the decrease of glass transition temperature ( T g ). In general, purple sweet potato powder contained the highest TPC (255.0 mg GAE  100 g DW −1 ) and antioxidant activity (1924.0 μmol TEAC  100 g DW −1 ), while orange powder had the highest beta‐carotene content (127.2 mg 100 g DW −1 ). Vacuum‐dried sweet potato powder, which has relatively higher antioxidant activity, could be a potential functional ingredient or natural colourant for the food industry.