Effect of cooking on nutritive and antioxidant properties of leafy vegetables consumed in Southern Côte d’Ivoire

Abstract

African leafy vegetables are valuable sources of nutrients especially in rural areas where they contribute substantially to protein, minerals, vitamins, fibre and other beneficial nutrients. Five leafy vegetable species (Basella alba, Colocasia esculenta, Corchorus olitorius, Solanum melongena and Talinum triangulare) that are used as soup condiments in Southern Côte d’Ivoire were subjected to cooking in order to evaluate the effect of this processing method on their nutritive value and antioxidant properties. The result of the study revealed that longer time of cooking (higher than 15 min) caused negative impact by reducing nutritive value but positive impact by reducing anti-nutrients such as oxalates and phytates. The registered losses at 15 min were as follow: ash (12.42 – 54.09 %), proteins (3.47 - 33.23 %), vitamin C (46.42 – 83.21 %), carotenoids (73.74 – 100 %) oxalates (19.29 – 59.86 %) and phytates (28.61 – 78.02 %).The average reduction of polyphenols content at 15 min of cooking was 9.95 – 59.43 %. Contrary to these reductions, a slight increase of fibres content was observed in the studied cooked leafy vegetables. Furthermore after 15 min of cooking time the residual contents of minerals were: calcium (119.92 – 512.70 mg/100g), magnesium (51.94 – 285.07 mg/100g), potassium (529.92 – 1721.18 mg/100g), iron (12.37 – 25.63 mg/100g) and zinc (11.53 – 25.03 mg/100g). All these results suggest that the recommended time of domestic cooking must be less than 15 min for the studied leafy vegetables in order to contribute efficiently to the nutritional requirement and to the food security of Ivorian population.