COMPARATIVE CHARACTERIZATION OF AQUEOUS STARCH DISPERSIONS BY LIGHT-MICROSCOPY, RHEOMETRY AND IODINE BINDING BEHAVIOR

Aqueous potato, wheat and pea starch dispersions (2 g dry starch/100 g dispersion) were prepared at different time-temperature conditions an d characterised by light microscopy of stained cryo-sections, amperome tric iodine titration and rheometry. Depending on the gelatinisation c onditions 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 f rom the granules and accumulation of amylose in the centre elf the gra nules. The iodine binding capacity of the starch systems was related t o the extent of swelling and solubilisation of starch and is therefore an appropriate indicator to follow the gelatinisation process. The fl ow behaviour was also sensitive to differences in the microstructure. The combination of light microscopy, iodometry and rheology successful ly allowed the extensive characterisation of the supramolecular struct ure of low concentration starch systems.