Effect of varying concentrations of phytate, calcium, and zinc on the solubility of protein, calcium, zinc, and phytate in soy protein concentrate

The phytate X Ca:Zn millimolar ratio was varied in a number of soy protein concentrates and subjected to a sequential pH treatment to simulate gastrointestinal conditions. In two independent studies, calcium was either decreased incrementally from 4.94 to 0.25 mmol or zinc was increased from 0.0036 to 0.55 mmol. At the lowest level of calcium, a significant increase (P 0.01) in soluble zinc and soluble phytate was observed at pH 5.5, due to the possible formation of a soluble calcium-phytate-zinc complex. Soluble zinc significantly increased (P 0.01) only when the level of zinc was raised to 0.55 mmol. Neither soluble calcium nor soluble phytate was altered at this level