Effect of cooking time on selected metals, oxalate and phytate contents of the raw and cooked lettuce from five farms in Ethiopia

Abstract

The effect of cooking time on mineral composition and anti-nutritional factors, oxalate and phytate, of lettuce grown in five farms of Ethiopia was investigated in this study by flame atomic absorption spectrometry, titrimetry, and spectrophotometrically, respectively. The work was focused in the evaluation of bioavailability of Ca, Fe and Zn by the molar ratios of [Phy]:[Fe], [Phy]:[Zn], [Ca]:[Phy], ([Ca][Phy])/[Zn]. The mineral composition was found to be: 1557–3171, Ca; 13.8–14.7, Mg; 0.7–2.8, Zn; 21.4–123, Fe; 3.94–9.41, Mn; 0.39–1.19, Cu; ND–0.24, Co; and 1.46–2.63, Ni; in mg/100 g in the raw samples. They all show decreasing on cooking except Fe, Zn and Ca which show significant increment depending on cooking time interval. The anti-nutritional factors in uncooked lettuce may present health-hazard potential, which in turn demands cooking for short time before consumption to eliminate the toxic effects of anti-nutritional factors.