Many foods have relatively high concentrations of multivalent ions, other than iron, e.g., calcium. The effectiveness of EDTA as an antioxidant could be diminished by the presence of calcium, because it can compete with the iron for binding to EDTA. EDTA has a high calcium ion-binding constant, although it is less than that of iron ions. Relatively high concentrations of calcium may bind the EDTA in the system, leaving iron the opportunity to associate with the emulsion droplets, thus resulting in oxidation of the lipid and instability of the emulsion.