Physical, thermal, mechanical and barrier properties of pearl millet starch films as affected by levels of acetylation and hydroxypropylation

Abstract

Starch-based films possess potential application in food packaging, due to their biodegradability, lower cost, stretchability and clarity. The aim of this work was to develop novel edible films from native, acetylated and hydroxypropylated pearl millet starches with improved flexibility, transparency and water barrier properties. Each film contained a fixed concentration of starch (3 g/100 g) and glycerol (30%, w/w based on starch weight). The effect of levels of acetylation (4% and 8%, w/w) and hydroxypropylation (10% and 30%, w/v) on the rheological, physical, thermal, mechanical and barrier properties of films was investigated. SEM results showed that modified starch films possessed smoother surface in comparison to native starch film (NF). Rheological evaluation depicted that filmogenic solution of 30% hydroxypropylated starch was more viscous than other solutions. Films containing 4% and 8% acetylated starches showed excellent moisture barrier property as depicted by their low water vapor permeability (WVP) and water solubility (WS). The extent of these improvements depended on the levels of acetylation. Elongation at break (%EAB) and transparency (%T) of 10% and 30% hydroxypropylated starch films were higher than NF and increased with increasing amount of propylene oxide. Glass transition temperature (Tg) was lowered by addition of modified starches in film formulation.