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

Abstract

SummaryThis 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 (Tg). 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.