Phytate‐calcium interactions with soy protein

Abstract Solubilities of mixtures of soy protein isolate, calcium and phytate were determined as a function of pH and molar ratio of the components. Below the isoelectric point, phytate and protein solubility profiles paralleled each other, indicating some type of protein‐phytate interaction. Addition of phytate shifted the isoelectric point and the minimum solubility to lower values. Between the isoelectric point and pH 6.5, the complex apparently dissociates; addition of phytate results in an increase in the maximum solubility of the phosphorus and the protein, as well as a shift in their solubility profiles. Calcium has no apparent effect on protein solubility in this pH region. Higher pH (>6.5) results in the formation of ternary protein‐calcium‐phytate complexes and a significant drop in calcium and phosphorus solubility, probably due to formation of insoluble calcium phytate salts.