Studying physical state of films based on casava starch and/or chitosan by dielectric and thermal properties and effects of pitanga leaf hydroethanolic extract

Cassava starch (CS) and chitosan (CH) are biopolymers used alone or blended (CS/CH) to produce films, thanks to their excellent film-forming properties. Their main physical properties have been characterized, but their physical and water state have not yet been studied. The objective of this research was to study the water and macromolecular physical state of CS, CH and CS/CH films by DSC and dielectric properties, after sorption isotherms determinations. Biopolymers and obtained films were also analyzed by SEM, FTIR, X-ray diffraction and gas permeability. Dielectric properties of active films containing pitanga leaves hydroethanolic extract were also analyzed. All films presented type II sorption isotherms. Glass transition temperature of films decreased with the increase of moisture content (X-w) following the Gordon and Taylor model. The dielectric constant behaves depending of the monolayer moisture content (X-m): increased linearly as a function of X-e when X-w > X-m. For X-w <= X-m, the dielectric constant remained constant. An exponential relationship between alpha-relaxation and Tg was calculated.

Automated summary

This study investigated the water and macromolecular physical state of cassava starch, chitosan, and their blend films through DSC and dielectric properties analysis. The results showed that the glass transition temperature of the films decreased with increasing moisture content, and the dielectric constant changed depending on the moisture content. When the moisture content was below a certain value, the dielectric constant remained constant.