Ascorbic Acid and Dehydroascorbic Acid Content of Tropical Root Crops from the South Pacific

Abstract

ABSTRACTThe total vitamin C content (ascorbic acid (AA) plus dehydroascorbic acid (DAA) was estimated by HPLC for sweet potato (Ipomoea batatas), taro (Colocasia esculenta), giant taro (Alocasia macrorrhiza), giant swamp taro (Cyrtosperma chamissonis), taro (Xanthosoma spp.), yam (Dioscorea alata), yam (D. esculenta), cassava (Manihot esculenta) and mean values were 23.6, 15.1, 16.9, 15.7, 13.6, 27.5, 20.3, and 14.9 mg/100g fresh weight, respectively. Standard titrimetric and colorimetric methods gave results only for AA which were generally comparable with HPLC. Drying at 40°C caused loss of AA which was not quantitatively converted into DAA. Storage of sweet potato at 25°C and 15°C for 28 days reduced the total vitamin C content by 17% and 15%, respectively; there was no significant decrease at 0°C. Cooking reduced the levels of AA and DAA by up to 70%.