Effects of cooking process on carotenoids and antioxidant activity of orange-fleshed sweet potato

Abstract Effects of boiling, steaming, microwaving, roasting and frying on proximate composition, carotenoids and antioxidant activities of orange-fleshed sweet potato (OFSP) were investigated. Retentions of 66.30–82.19% of β-carotene contents were observed after boiling (15–35 min), steaming (15, 35 and 45 min) and microwaving (15 min). High retentions of (9Z)-β-carotene were noted after all cooking processes, being 515.40% after steaming at 45 min. α-carotene was highly retained after boiling at 15–35 min (103.77–106.74%). A high retention of 91.37% in total polyphenol contents was noted after steaming (35 min), whereas 98.98–102.36% of vitamin C was retained after steaming (15–45 min) and microwaving (15 min). All cooking processes improved antioxidant activities of OFSP, and the correlation analysis between carotenoid contents and antioxidant activity suggested that antioxidant activity could be attributed to the higher contents of (9Z)-β-carotene. It was suggested that boiling and steaming are preferable to maintain carotenoids and antioxidant activities of OFSP.