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

The 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%.