Films from corn, wheat, and rice starch ghost phase fractions display overall superior performance than whole starch films

In a previous study, gelatinized corn starch dispersions (GSD) containing different (similar to 7-59.6%) ghost phase fractions (GPF), i.e., insoluble amylopectin-rich remnants with glycerol added as plasticizer were cast and dried to obtain films. GPF had both positive and negative effects on the films' properties, but GPF of around 20-30%, provided films with good and balanced overall properties ((elongation-at-break (EB), ultimate tensile strength (UTS), opacity, and water vapor permeability (WVP)). Here, corn, wheat, and rice GSD were prepared containing GPF of 63.6, 61.3, and 58.2%. The GPF was separated from GSD, and films were prepared with solely the GPF and with the whole GSD. Ghost phase fraction films (GPFF) exhibited higher hydrophobicity and EB, lower WVP and retrogradation than those obtained from the whole gelatinized starch dispersion films (GSDF), with only UTS exhibiting lower values. It was postulated that the underlying reason for the improved overall performance displayed by the GPFF was that they practically did not retrograde, due to the depletion of the amylose-rich viscous continuous phase, and that the ghosts played an important role as physical fillers imparting elasticity and as physical barriers hindering the transport of water. The ghosts' particle size and concentration affected the surface morphology, accounting for the differences in properties found between the corn, wheat, and rice GPFF.