Effect of Boiling on Chemicals, Phytochemicals and Nutritional Composition of Solanum nigrum L. Leaves Harvested in Abidjan (Côte d’Ivoire)

Abstract

Aims: In tropical Africa, leafy vegetables are traditionally cooked and eaten as a relish together with a starchy staple food. The current study aimed to evaluate the influence of boiling on bioactive, proximate and antinutrients compounds in Solanum nigrum leaves.
 Methodology: The leaves were subjected to boiling in pressure cooker for 10, 15 and 20 min and proximate composition, minerals, nutritive and anti-nutritional components were determined according to standard methods for nutritional guidelines.
 Results: The result of the study revealed that longer time of boiling (higher than 10 min) caused negative impact by reducing nutritive value but positive impact by reducing anti-nutrients. The registered losses (p < .05) at 10 min were as follows: ash (12.37%), proteins (33.69%), vitamin C (11.23 mg/ 100 g), polyphenols (125.41 mg/ 100 g) Tannins (81.96 mg/ 100 g) and Flavonoids (14.03 mg/100 g). The average increase of fibers content was (39.41%). Furthermore, after 10 min of boiling time the residual contents (p<0.05) of minerals was: Calcium (1079±29.04 to 386±78 mg/ 100 g), Phosphorus (405..24±10-508.88±2.58 mg/ 100 g), Iron (33.48±0.93–44.50±1.23 mg / 100 g) and Magnesium (572.78±19.76–662.99±27.23 mg/ 100 g).The antinutrient composition for oxalic acid were ranged 72.61±6.29 to 223.67±6.35 mg/100 g. The different ratios sodium / potassium (<1) and oxalates/calcium (<2.5) were under the respective critical value for all boiling.
 Conclusion: These results suggest that the recommended time of domestic cooking must be less than 10 min for the studied leafy vegetables in order to contribute efficiently to the nutritional requirement and to the food security of Ivorian population.