Effects of acetylated and octenyl-succinated starch on properties and release of green tea compounded starch/LLDPE blend films

摘要

Modified starch improved compatibility and modified properties of thermoplastic starch (TPS)/LLDPE blends, producing lower environmental impact food packaging. Effects of modified starch on functional properties and release behavior of green tea (GT) extract compounded with TPS were investigated to produce active film packaging. LLDPE was first extruded with native (NS), acetylated (AS) and octenyl-succinated (OS) starch. The structure of blown-extruded films showed that AS and OS improved compatibility between starch and LLDPE. Modified starch gave better mechanical properties (13-26% and 3-15% for tensile strength and elongation, respectively) and had a more homogeneous structure than NS. Hydrogen bonding between GT and starch modified the compatibility of blend films with surface roughness (9-37%) and greatly increased wettability (3-9%). Surface roughness derived from atomic force microscopy modified wettability in TPS/LLDPE films and controlled release behavior in aqueous media (water, 3% acetic, 10% ethanol and 95% ethanol). High ethanol medium (95% ethanol) accelerated the release rate of GT due to strong affinity of phenolic compounds for the medium and interaction of ethanol with polymer matrices that enhanced diffusion. Barrier properties of blend films were controlled by the hydrophilicity and microstructures of the matrices. AS, OS and GT modified the contraction and crystallization behavior of polyethylene chains as revealed by shifting of infrared adsorption bands and differential scanning calorimetry derived crystallinity, respectively. Modified starch strongly altered the molecular organization of polymers and microstructures and subsequently impacted properties of TPS/LLDPE films.