The antioxidant property of home-cooked orange-fleshed and purple-fleshed sweet potato

Abstract

One property inherent to sweet potato because of the presence of phytochemicas is its antioxidant property. As proven by researches, antioxidant property is affected by cooking. This study determined the effect of four home cooking methods: steaming, boiling, baking, and frying on the antioxidant property of orange-fleshed and purple-fleshed sweet potatoes. The antioxidant property of raw and cooked we measured samples for their Total Phenolic Content (TPC) using Folin-Ciocalteu assay and their antioxidant activity based on the EC50 value of the DPPH assay. The TPC of orange-fleshed sweet potato was significantly increased by boiling and steaming. Baking and frying decreased the TPC of the orange-fleshed. The TPC of the purple-fleshed variety was not affected by the cooking methods but compared to the orange-fleshed, the TPC of the purple variety is significantly higher in both the raw and cooked forms. Based on the result of the DPPH assay, cooking significantly affected the antioxidant activity of both varieties (p<0.05). Steaming gave the highest increase for both varieties. Boiling caused the lowest increase for the orange-fleshed but didn’t give a significant effect on the antioxidant activity of the purple-fleshed. Comparing the two varieties, the raw and cooked purple-fleshed sweet potato have better antioxidant activity based on DPPH assay except for the steamed samples wherein the antioxidant activity of steamed orange-fleshed sweet potato is significantly higher (p<0.05) than that of the purple variety. It can be concluded that steaming is the best cooking method for the two sweet potato varieties. Keywords: Anti-oxidant, cooking, sweet potato, total phenolic content.