Thermal dissolution of maize starches in aqueous medium

Starches are insoluble in neutral water at room temperature. However, if they are heated beyond the boiling point of water in a closed container, they eventually dissolve. The dissolution profile depends on the type of starch. The dissolution processes of maize starches were monitored in real time by measuring the transmittance of starch dispersion/solution while it was heated. It was found that the dissolution of starches in water results from the degradation of the two components of starches, amylopectin and amylose. Starches from both normal maize and waxy maize were fully dissolved in water when their aqueous solution was heated to approximately 174 °C. Upon cooling to room temperature, amylopectin remained in a solubilized state while amylose molecules were retrograded. For starch solutions that have been heated to higher than 191 °C, the color turned brown and the retrogradation of amylose was not observed.

► Heating effect on the dissolution of starch in water was investigated.
► The solubilization process of starch was monitored with a laser turbidometer.
► A clear starch solution was obtained when heated to around 175 °C.
► Significant thermal degradation was observed at higher than 155 °C.
► Above 185 °C, no more polymeric starch exists in the solution.