Effects of controlled storage on thermal, mechanical and barrier properties of plasticized films from different starch sources

Thermal, mechanical and barrier properties of corn, cassava and yam starch films were determined and the behavior of these three starches films under a controlled storage (64% RH and 20 degrees C) was compared. Glass transition (T,) in all unplasticized films was higher than in plasticized, and during storage, T-g decreased, except for samples with 40 g glycerol/100 g starch. Crystallinity was affected by plasticizer concentration and storage time; in unplasticized samples the increase in crystallinity was higher than in plasticized ones during storage, thus, unplasticized stored samples become more brittle and less permeable during storage. Unplasticized films showed water vapor permeability (WVP) values ranged from 6.75 to 8.33 x 10(-10) g m(-1) s(-1) Pa-1. These values decrease when glycerol content reached at 20 g/100 g starch because a more compact structure was formed and, then, at 40 g glycerol/100 g starch, WVP increased because film matrixes became less dense. (c) 2005 Elsevier Ltd. All rights reserved.