The adsorption of orthophosphate onto casein-iron precipitates

•Solubility of precipitated casein-iron complexes can be improved by orthophosphate.•Orthophosphate can adsorb onto precipitated casein-iron complexes.•This adsorption results in re-solubilisation of the complexes.•Soluble casein-iron-orthophosphate complexes could be used as a novel fortificant.

This study explored the interactions of orthophosphate with casein-iron precipitates. Casein-iron precipitates were formed by adding ferric chloride at ≥10 mM to sodium caseinate solutions ranging in concentration from 1 to 3% (w/v). The addition of different concentrations of orthophosphate solution to the casein-iron precipitates resulted in gradual adsorption of the orthophosphate, causing re-dispersion of the casein-iron complexes. The interactions of added orthophosphate with iron in the presence and absence of caseins are postulated, and new mechanisms are proposed. The re-dispersed soluble complexes of casein-iron-orthophosphate generated using this process could be used as novel iron fortificants.