Effect of mechanical activation on starch crosslinking with citric acid

The aim of this research was to investigate the influence of mechanical activation in a rotor-stator device on starch crosslinking with citric acid and the properties of the films obtained by the casting method. Two methods of preparation of the casting hydrogels were used: involving the introduction of chemical reagents before and after the mechanical activation. The films from the initial and mechanically activated hydrogels were characterized using optical and AFM microscopy, X-ray diffraction and FTIR-spectroscopy. The di-esterification degree, opacity, tensile properties and moisture resistance of the films were also studied. Mechanical activation of the starch hydrogels made it possible to make the films smoother and more transparent and to increase their tensile strength and moisture resistance. Pre-activation of the hydrogels without reagents showed better film performance than activation in the presence of citric acid.