Physical properties and stability of starch-gelatin based films as affected by the addition of esters of fatty acids

Cassava starch films containing 25 and 50% (in the polymer blend) of bovine gelatin were obtained using glycerol (30%) as plasticizer. Film formulations were also obtained with 15% of lipid (blend of fatty acid-glycerol esters). Microstructural and physical (optical, barrier and mechanical) properties were analyzed in order to compare blend films with neat starch or gelatin films. The incorporation of gelatin and lipids to glycerol-plasticized cassava starch films notably affected their physical properties, while they showed polymer-phase separation and a lipid-dispersed phase. Gelatine incorporation gave rise to harder films with greater resistance to break and extensibility, while the lipids decreased film hardness and resistance but enhanced the stretchability, especially in films with 50% gelatin content. Likewise, lipids improved water barrier properties of the films, but they impaired the oxygen permeability at the same time as they decreased the film gloss and transparency. After 5 weeks of storage, all the films became harder and more resistant to break, especially those which did not contain lipids, which enhanced the films' extensibility during storage. Cassava starch films with 50% gelatine, both with and without lipids, exhibited very adequate properties for food coating or packaging. (C) 2015 Elsevier Ltd. All rights reserved.