Once a starch solution reaches around sixty degrees the granules start to swell and the heat breaks the hydrogen bonds.
Further heating to eighty five degrees and the amylase and amylopectin are completely dispersed in water and a colloid system known as a SOL is produced when the starch granules split open. With the increased viscosity amylase molecules leak out.
When the SOL is cooled hydrogen bonds re-establish in a loose network and a gel is formed. Amylose gels more easily than amylopectin.