Mineral Profile and Effect of Phytic Acid on Mineral Bioavailability in Phaseolus spp Cultivated in Togo

Beans of the genus Phaseolus constitute a major source of essential minerals in human diets, particularly iron, zinc, and calcium. This study evaluated the mineral composition and potential bioavailability of 48 local varieties cultivated in Togo. Magnesium, phosphorus, calcium, iron, and zinc contents were determined by X-ray fluorescence, while phytic acid was quantified using the Folin colourimetric method. Significant differences were observed among samples for P, Ca, Fe, and Zn (p < 0.001), in contrast to Mg (p = 0.638). Concentrations ranged from 5,249 to 9,702 mg·kg⁻¹for Mg, 4,203 to 10,991 mg·kg⁻¹for P, and 3,100 to 5,378 mg·kg⁻¹for Ca. Fe and Zn contents ranged from 48.1 to 107 mg·kg⁻¹and from 59.8 to 106 mg/kg, respectively. A strong positive correlation was found between Fe and Zn (r = 0.77; p < 0.001). Bioavailability indicators revealed substantial heterogeneity, with PA/Fe ratios ranging from 7.61 to 27.68, PA/Zn from 8.07 to 29.86, and PA/Ca from 0.10 to 0.39. The PA×Ca/Zn index ranged from 764.41 to 2,854.04. Principal component analysis showed a clear structuring of bean samples according to their mineral profile and seed coat colour. These results highlight a contrasting nutritional potential, strongly influenced by the effect of phytate on mineral bioavailability.