Comparative study on the nutrients and anti-nutrients composition of the peels and flesh of sweet potato (Ipomoea batatas l.)

Abstract

The increasing incidence of food shortages and nutritionally related diseases in the world has made it imperative to carry out nutritional studies on food materials. The proximate composition, minerals and vitamins, as well as the anti-nutrient constituents of the peels and flesh of sweet potato were determined. The peels were found to contain higher levels of crude protein (8.79 %), lipid (4.5 %), fibre (2.00 %) and ash (4.00 %) than the flesh (4.83 %, 0.1 %, 1.0 % and 3.0 % respectively) while the later had higher levels of moisture (71.29 %) and carbohydrate (91.07 %). The flesh was also higher in β-carotene (3.59 mg/100g) and vitamin A (4.30 IU) than the peels (1.26 mg/100g and 1.60 IU respectively), while the peels were higher in vitamin C (20.63 mg/100g). The peels were also found to contain higher levels of the minerals – iron (43.95 mg/100g), magnesium (20.63 mg/100g), manganese (0.07 mg/100g), calcium (40.41 mg/100g) and phosphorus (98.95 mg/100g) than the flesh (25.65 mg/100g, 2.11 mg/100g, 0.00 mg/100g, 16.84 mg/100g and 72.95 mg/100g respectively). The flesh had minimal levels of the anti-nutrient compounds - hydrocyanic acid (17.28 mg/100 g), tannins (385.19mg/100g), oxalate (total with soluble) (61.60 mg/100g) and phytate (557.26 mg/100g) while the peels showed higher levels of these compounds (21.60 mg/100g, 533.33 mg/100g, 433.60 mg/100g and 755.70 mg/100g respectively). Sweet potato tubers and peels are an excellent source of calories, vitamin C and beta carotene, with considerable amounts of protein and macro minerals. It is recommended that the peels of sweet potato be processed into animal feed and not discarded as garbage. Also, when properly processed to reduce anti-nutrient contents, the sweet potato peels can be consumed just as the flesh, thus can reduce malnutrition and other nutritional related diseases.