[Binding of lead and copper ions to ethanol-insoluble substances from cooking potatoes]

The binding of Pb2+- and Cu2+-ions to ethanol-insoluble substances from three sorts of raw or cooked table potatoes in aqueous suspension is investigated. Moreover, analogous tests on the binding of Pb2+-ions to glucose-6- and glucose-1-phosphate as well as to phosphoric acid are performed. The determination of the free cations in the equilibrium solutions is directly carried out by means of ion-specific electrodes in consideration of the pH-influence. In view of nutrition physiology raw and cooked potatoes are capable, as well as vegetables, of binding Pb2+ and Cu2+ ions, due to their content of pectins with an esterification degree found to be in the range of 50-56% and 42-48%, respectively. The binding capacity of the ethanol-insoluble substances does not only base on their content of pectin-carboxyl groups but also on other macromolecular components. Among the metabolic degradation products of potato starch only free phosphoric acid is capable of binding Pb2+ ions.