While interfering ions in water play a crucial role in altering starch's adsorption behavior on hematite, their effects on starch gelatinization properties have not been fully understood. The purpose of this research is to investigate how Ca²⁺ affects the morphology of caustic-gelatinized starch and its effectiveness in flocculating iron oxides. A series of tests and measurements were employed, including batch flotation, sedimentation, turbidity, viscosity, zeta potentials, Fourier Transform Infrared, powder contact angle, and surface force calculations. The results demonstrate that calcium ions inhibit starch gelatinization, as evidenced by increased turbidity and reduced viscosity. This reduces floc size and settling rate, ultimately weakening starch's flocculation efficiency. The mechanism likely involves calcium-mediated re-entanglement of stretched starch chains through interactions with the functional sites generated during alkaline gelatinization. The formation of Ca-starch crosslinking diminishes the starch gel's ability to flocculate fine particles.