High resolution imaging of the microstructure of maize starch films

Glycerol-plasticised and non-plasticised cast films were prepared from maize starch suspensions that had been heated under reflux for different periods of time. Light microscopy (LM) and atomic force microscopy (AFM) have been used to observe the morphology of the starch films. In general, LM and AFM topographic images of corresponding non-plasticised films were similar. AFM topographic images of plasticised films revealed differences associated with the retarding effect of glycerol on the gelatinisation process. Relatively high B-type crystallinity indices were determined for plasticised films, independently of the heating conditions to which the suspensions had been submitted. AFM topographic images of plasticised films at higher magnifications revealed smooth and rough domains, that were detailed by phase contrast imaging.