Amaranth protein films reinforced with starch nanocrystals

CONDÉS, MARÍA CECILIA; AÑÓN, MARÍA CRISTINA; MAURI, ADRIANA; DUFRESNE, ALAIN

Washington

Congreso; TAPPI International Conference on Nanotechnology for Renewable Materials; 2011

Starch nanocrystals are promising as a new class of reinforcing material for the preparation of nanostructured composites. In this work, nanocrystals were prepared from waxy maize and wheat starch and used to modify amaranth protein films (Amaranthus hypochondriacus). The mechanical properties, water vapor permeability (WVP), water uptake (WU), colour and morphology of such biocomposites were investigated and compared to those of unfilled protein films. The water content and thickness were respectively 20 % and 70 m, in agreement with film processing conditions. The mechanical properties of nanocomposites were strongly modified. The elongation at break gradually decreased with the nanostarch content regardless its origin. When increasing the wheat nanocrystal content over 3%, the tensile strength and Young’s modulus dramatically increased. This effect was also observed but to a lesser extent for waxy maize nanostarch. The WVP of the films was improved upon adding waxy maize nanocrystal until a rate of 6% and then the WVP was similar to protein films. For films reinforced with wheat nanostarch the WVP was improved for filler content higher than 9%. For both nanostarchs, the WU decreased, and the films color was similar to the one of unfilled protein films. The cryofractured surfaces of films were observed by scanning electron microscopy (SEM). The surface of nanocomposite films displays a fractured lamella structure. This is more evident when increasing the starch content up to 12% and then for higher filler content it is rough. Different structures and improved mechanical and barrier properties for starch nanoparticles extracted from both starch sources.