Preparation of iron/zinc bound whey protein concentrate complexes and their stability

Food fortification is the most cost effective, sustainable and optimal approach in the battle against iron and zinc deficiencies. Iron/zinc, being members of the transition metal series, are highly reactive and poses numerous challenges with respect to physicochemical stability of fortified foods. Whey proteins concentrate (WPC) produced as the principal byproduct of cheese or casein manufacturing is widely used as food ingredient. Among the various technologies explored, iron/zinc binding to milk proteins has long been understood and applied. Therefore, method for the preparation of WPC - mineral (iron/zinc) complex was standardized on the basis of maximum mineral binding ability of proteins. Method involving ultrafiltration and diafiltration (repeated washing to remove free mineral from retentate) has been standardized. Structural modification upon mineral binding was confirmed by RP-HPLC chromatograms. Both iron and zinc bound WPC complexes possessed good stability (resistance towards release of bound mineral) under different processing conditions. However, zinc bound WPC showed better heat stability and lower pH and ionic stability compared to iron bound WPC. The final protein - mineral complexes could be used as a suitable organic fortificants for various food applications with better solubility.