Optimization of Water Cooking of Sweet Potato (Ipomea batatas) Leaves and Characterization of Three Nutritional Interest Molecules (Folic Acid, Iron and Phytate)

Abstract

Sweet potato (Ipomea batatas) leaves are among the leafy vegetables most consumed by Ivorian population. In order to preserve iron and folic acid, and to eliminate phytates, a study of optimization of water cooking of these leaves was conducted. Response surface methodology was employed to describe the effects of cooking time and leaf quantity on iron, folic acid and phytate contents of sweet potato leaves using a central composite design. Response surfaces and isoresponse curves were plotted to visualize areas of interest (optimal points). Results showed that the experimental data were adequately fitted into the second-order polynomial model. Cooking time had significant effects (P < .05) on folic acid and phytate contents. The effect of leaf quantity was significant (P < .01) on the three response variables. In addition, the optimal points were located in areas of the experimental domain where iron and folic acid contents were high. Therefore, three optimal conditions for water cooking (cooking time, leaf quantity) were identified: (10 min, 400 g), (7.93 min, 300 g) and (22.07 min, 441.4 g). Under these conditions, iron and folic acid contents (mg/100 g) were: (49.17, 12.58), (37.00, 16.27) and (48.77, 11.26), respectively. These results could be exploited to formulate iron and folic acid supplementation products from sweet potato leaves.