Changes in Anti-Nutrients Contents of Edible Vegetables Under Varied Temperature and Heating Time
Three edible vegetables, Pterocarpus mildbraedii (mkpafere), Lasianthera africanum (editan) and Piper guineense (odusa) consumed by people of Akwa Ibom State, Nigeria were purchased from Akpan Andem market in Uyo, the State capital. The vegetables were analysed for the presence of anti-nutrients (HCN, tannin, phytate and oxalate), and the effect of heating at 50 °C for 5 minutes, 90 °C for 5 minutes and 90 °C for 15 minutes in water. Tannins among the anti-nutrients, recorded highest level for all vegetables. At 50 °C for 5 minutes, HCN, tannin, phytate, total oxalate and soluble oxalate respectively, reduced by 17.6%, 9.1%, 11.0%, 9.5% and 23.8% (Pterocarpus mildbraedii), 13.9%, 6.1%, 1.4%, 13.8% and 13.0% (Lasianthera africanum), and 14.1%, 35.1%, 5.8%, 15.4% and 22.2% (Piper guineense). The percentage reductions for HCN, tannin, phytate, total oxalate and soluble oxalate were 23.6%, 53.4%, 25.5%, 56.2% and 52.4% (Pterocarpus mildbraedii), 43.5%, 25.0%, 51.8%, 37.9% and 52.2% (Lasianthera africanum), 50.0%, 51.9%, 40.2%, 23.0% and 33.3% (Piper guineense) respectively, after heating at 90 °C for 15 minutes. The study revealed reduction of anti-nutrients on heating; and 90 °C as optimum temperature, with heating time of not less than 15 minutes for processing the vegetables.