Edible packaging from hydroxypropyl thermoplastic cassava starch, agar and maltodextrin blends produced by cast extrusion

Edible packaging from hydroxypropyl cassava starch with different degrees of substitution (DS), agar and maltodextrin films was produced by conventional cast extrusion. Microstructures showed hydrophobic agar aggregates (100-200 mu m) dispersed in film matrices, giving nonsmooth surfaces that enhanced wettability (17%-31%). Higher DS increased interaction between agar and maltodextrin via hydrogen bonding due to greater plasticisation and enhanced formation of agar networks. Lower DS starch showed instability with lower tensile strength (23% of higher DS), giving poor processability that was greatly improved by agar (20%). Water vapour and oxygen permeability depended on microstructures and hydrophilic-hydrophobic properties of the matrices which were decreased by 25% and 58% with combined agar and maltodextrin, respectively. Crystallinity of the films depended on plasticisation, with enhanced mobility that reduced transparency. Agar and maltodextrin inhibited recrystallisation of starch. Findings suggested that higher DS starch and agar enhanced extrusion processability, while maltodextrin increased plasticisation and reduced network strength.

Automated summary

The study investigated the effects of different degrees of substitution of hydroxypropyl cassava starch with agar and maltodextrin on the microstructure and properties of edible packaging films. The findings suggested that higher DS starch and agar improved extrusion processability, while maltodextrin increased plasticization and reduced network strength, affecting the overall performance of the films. The combination of agar and maltodextrin also influenced the water vapor and oxygen permeability of the films, showing potential for enhancing the properties of the packaging materials.