Starch is not soluble in water ??
It forms colloid in aqueous medium called as micelles. Iodine reacts with both amylose and amylopectin, but the former produces a complex that gives an intense blue colour and masks the violet colour of the complex formed by the latter. As a result, we observe a blue colour when starch reacts with iodine. This colour complex dissociates on heating and reforms again after cooling.