Physical and mechanical properties of starch films: the role of the cross-linking mechanism through iodine binding capacity

Abstract

In this study, a better knowledge of the influence of cross-linking mechanism on the mechanical properties of starch films is presented. Thus, waxy starch and cassava starch films, cross-linked with trisodium trimetaphosphate (STMP), were produced and characterized concerning their morphology, transport, and mechanical properties. Starch cross-linking was verified by RAMAN spectroscopy and by iodine binding capacity (IBC) values, which were determined by color analysis of digital images. Although cross-linking affects the morphology and crystallinity of the films, it was not observed a relationship between the mechanism of the cross-linking reaction of the starch chain (amylose-amylopectin and amylopectin-amylopectin) and the transport properties. The lower Young Modulus and IBC value and the higher elongation at break observed for cross-linking cassava starch films relative to control and waxy films indicate that cross-linking mechanism influences the mechanical properties of starch films and should be considered to tailor the final properties of packaging and biobased products.