Development of flexible zein-wax composite and zein-fatty acid blend films for controlled release of lysozyme

The aim of this study was controlled release of lysozyme by modification of hydrophobicity and morphology of zein films using composite and blend film making methods. The incorporation of beeswax, carnauba or candelilla wax into films at 5% (w/w) of zein gave composite films containing amorphous wax particles, while incorporation of oleic acid into film at 5% of zein caused formation of blend films containing many spherical zein capsules within their matrix. The lysozyme release rates of composites reduced as the melting point of waxes increased. The composites and blends showed 2.5 to 17 fold lower lysozyme release rates than controls. The films were effectively plasticized by using catechin. The catechin also provided antioxidant activity of films (up to 69 μmol Trolox/cm2) and contributed to their controlled release properties by reducing film porosity. The films showed antimicrobial activity against Listeria innocua. This work showed the possibility of obtaining advanced edible films having flexibility, antimicrobial and antioxidant activity and controlled release properties.

► Mixing waxes or oleic acid into zein gave composite and blend films, respectively. ► Composite and blend films have lower lysozyme release rates than zein films. ► The lysozyme release rates can be changed by using different waxes in composites. ► Zein based films could effectively be plasticised with phenolic compound catechin. ► Catechin also contributed to controlled release properties by reducing film porosity.