Comparative Characterisation of Aqueous Starch Dispersions by Light Microscopy, Rheometry and Iodine Binding Behaviour

Abstract

Aqueous potato, wheat and pea starch dispersions (2 g dry Starch/100 g dispersion) were prepared at different time-temperature conditions and characterised by light microscopy of stained cryo-sections, amperometric iodine titration and rheometry. Depending on the gelatinisation conditions and the type of starch, a broad range of microstructures was obtained ranging from limited swelling to complete disintegration of starch granules. The swelling was accompanied by leaching of amylose from the granules and accumulation of amylose in the centre of the granules. The iodine binding capacity of the starch systems was related to the extent of swelling and solubilisation of starch and is therefore an appropriate indicator to follow the gelatinisation process. The flow behaviour was also sensitive to differences in the microstructure. The combination of light microscopy, iodometry and rheology successfully allowed the extensive characterisation of the supramolecular structure of low concentration starch systems.