Composite and nanocomposite films based on amaranth biopolymers

The use of amaranth starch granules and nanocrystals as possible reinforcement of amaranth proteins films was analyzed. Starch granules and protein isolates were extracted of amaranth grain, and nanocrystals were prepared by acidic hydrolysis from starch. Films were prepared by casting aqueous dispersions containing amaranth protein isolate (API, 5% w/v), glycerol (1.25% w/v) and different concentrations of starch granules (0-30 wt% relative to API) and nanocrystals (0-12 wt% relative to API). All films were homogeneous, translucent and slightly brownish, with a general visual appearance similar to the control amaranth protein film. While it was possible to prepare films in which the starch granules retain their native structure after being processed, the presence of these particles did not improve the film properties. Only the addition of starch nanocrystals improved their tensile strength and water vapor permeability as well as their water susceptibility, probably due to their nanosize, uniform distribution and the strong interactions that developed with protein matrix. (C) 2017 Published by Elsevier Ltd.