Effect of relative humidities on microstructural, barrier and mechanical properties of yam starch-monoglyceride films

Abstract

The effect of monoglyceride on microstructural, barrier and mechanical properties of casted yam starch films were investigated in different relative humidities (RH) and compared with glycerol-starch films. A single screw extruder was used to produce the starch - monoglyceride complex before film production and this process was effective to inhibit the phase separation in films. The addition of the hydrophobic compound reduced hydrophobicity, transparency and water vapor permeability of films. This later value for starch-glycerol film (1.7 × 10-10 g Pa-1 s-1 m-1) was higher than starch (1.2 × 10-10 g Pa-1 s-1 m-1) and monoglyceride-starch films (1.0 × 10-10 g Pa-1 s-1 m-1). Films containing glycerol had higher relative crystallinity (B and VH) with a slight increase at higher RH values, while for monoglyceride films, the crystallinity was constant. Monoglyceride-starch films presented poor mechanical properties when compared to glycerol-starch ones but they presented a stable behavior under different relative humidities.