Zinc bioavailability in different beans as affected by cultivar type and cooking conditions

Zinc bioavailability was studied in five cultivars of beans (Phaseolus vulgaris, L): white (Ouro Branco), black (Diamante Negro), and brown (BRS Radiante, Pérola and Talismã) cooked with or without soaking water. The cooked bean flours or ZnCO₃ were added to the test or control diets to provide 15 mg Zn/kg diet and were fed to weaning Wistar male rats for 42 days. Blood and femur were collected for analyses of plasma and erythrocyte Zn, bone weight and bone/dietary mineral ratio. Zinc bioavailability of Ouro Branco bean cooked with soaking water was higher than the other cultivars and similar to the control diet. Talismã without soaking water showed the lowest values for most of the parameters analyzed. Zinc bioavailability was not affected neither by the cooking process itself nor by the contents of phytate, tannins and dietary fiber, but it varied according to the bean cultivar and the phytate × calcium:zinc molar ratio.