Interactions among calcium, zinc and phytate with three protein sources

Various combinations of calcium (4.94 mmol), zinc (0.0071 mmol) and phytate (0.284 mmol) were added either to soy concentrate, casein or torula yeast to determine effects of their interaction on in vitro solubility of protein, calcium, zinc, and phytate (PA). Two Ca sources, calcium carbonate (CaCO3) and calcium-citrate-malate complex (CCM) were used. Two pH levels, 2.0 and 5.5, were used to simulate gastrointestinal pH conditions. An increase in pH significantly reduced (P less than 0.01) Zn solubility in all treatments with all protein sources. The solubility of Ca and PA were significantly decreased (P less than 0.01) when both components were present probably due to formation of insoluble Ca-PA complexes. At pH 5.5, with casein and yeast proteins, Zn was significantly more (P less than 0.01) soluble in samples with CCM, in the absence of PA, than in those with CaCO3.