PROXIMATE AND PHYTOCHEMICAL COMPOSITIONS OF DIFFERENTLY PROCESSED SWEET POTATO (Ipomoea batatas) PEEL MEAL

Abstract

This study investigated the effects of different processing methods (raw, boiled, fermented and dried) on nutritional composition and antinutritional factors of sweet potato (Ipomoea batata) peel. The differently processed sweet potato peels were analysed for proximate and phytochemical compositions in triplicates. The raw and processed sweet potato peels showed significant differences (P<0.05) in the contents of the moisture, crude protein, crude fibre, ash, calcium and phosphorus. The crude protein, ether extract and calcium contents of the raw samples were significantly higher than those of the processed samples. Crude fibre in sun-dried samples was significantly higher (P<0.05) than that of the other processing methods. Nitrogen Free Extract was significantly higher (P<0.05) in the processed compared to the raw samples. The ash content was highest in raw sample (4.12 %) and lowest in the fermented sample (2.67 %). All the processing methods showed significant effects (P<0.05) on the calcium and phosphorus contents of sweet potato peel. The antinutritional constituents present in sweet potato peel showed that the highest value for oxalic acid was in fermented peel. Flavonoids, tannins, hydrogen cyanide and phytic acid levels were higher (P<0.05) in the raw sample compared to the processed sweet potato peel. Based on the results of this study, fermentation and drying of sweet potato peel were most effective in reduction of antinutritional factors without severe effects on nutritional composition and are therefore recommended.