An iron binding assay to measure activity of known food sequestering agents: studies with buttermilk solids

A method enabling the measurement and differentiation of both ferrous (Fe2) and ferric (Fe3+) binding was developed to assess the relative sequesteri ng power of known iron chelators and buttermilk solids (BMS). Fe2+ and Fe3 chelation by EMS (0.1-10.0 mg), phytic acid, ethylenediaminetetraacetic ac id (EDTA) and citric acid (0.1 mM) was measured using a modification of a f erric-thiocyanate method. Fe2+ and Fe3+ was determined from the amount of u nbound ferric-thiocyanate following incubation with chelator. The assay was optimized for polarity of solvent and pH. Fe2+ and Fe3+ binding by sequest ering agents was, in descending order of affinity to be phytic acid > EDTA > EMS > citric acid. Known food iron chelators had a higher affinity toward s Fe3+, while EMS had a higher affinity towards Fe2+. EMS also demonstrated an excellent iron solubilization property through iron binding activity. ( C) 2001 Elsevier Science Ltd. All rights reserved.