Impact of the Coating Process on the Molecular Structure of Starch-Based Barrier Coatings

Molecular analysis of starch structure can be used to explain and predict changes in physical properties, such as water vapor and oxygen barrier properties in packaging materials. Solution casting is a widely used technique to create films from starch formulations. This study compared the molecular properties of these standard films with those of experimental coatings applied to paper in laboratory-scale and pilot-scale trials, with all three techniques using the same starch formulation. The results revealed large differences in molecular structure, i.e., cross-linking and hydrolysis, between films and coatings. The main differences were due to the shorter drying time allowed to laboratory-scale coatings and the accelerated drying process in pilot trials owing to the high energy output of infrared dryers. Furthermore, surface morphology was highly affected by the coating technique used, with a rougher surface and many pinholes occurring in pilot-scale coatings, giving lower water vapor permeability than laboratory-scale coatings. (C) 2014 Wiley Periodicals, Inc.