Effect of drying temperature and extent of particle dispersion on composite films of methylcellulose and zein nanoparticles

Abstract

Methylcellulose (MC) composite films containing zein nanoparticles (ZNP) are weakened at higher ZNP concentrations and neutral pH conditions because of ZNP aggregation. Accordingly, this study determined the effect of stabilizing additives and drying temperature on the microstructure and physical properties of films at high particle concentrations (ZNP:MC = 1:6). Films prepared at pH 6.5 exhibited large ZNP aggregates, decreasing tensile strength and elongation at break by 30–50% while also increasing water vapor permeability. Addition of poly(ethylene glycol) or oleic acid greatly reduced film tensile strength, and only poly(ethylene glycol) improved extensibility. Tensile strength, elongation at break, and water vapor permeability were all improved by a combination of carrageenan and the surfactant Tween 20 among films prepared at low temperature. Microscopic observations also showed improved dispersion of ZNP in films after adding carrageenan and Tween 20. However, drying films at 321 K with these additives led to contraction and deformation. Combined Tween 20 and carrageenan were necessary for composite film improvements, restoring mechanical and vapor barrier properties to those of pristine MC films. Use of stabilizers would then expand the conditions for using ZNP within MC composites for active film applications without limiting mechanical or barrier properties.