Improvement of barrier and mechanical properties of whey protein
isolate based food packaging films by incorporation of zein
nanoparticles as a novel bionanocomposite
In this study, whey protein isolate (WPI) based bio-nanocomposite films embedded with zein nanoparticles
(ZNP) were prepared by solution casting. Nanoparticles were coated with sodium caseinate to
obtain a uniform distribution in the films. The mechanical, water vapor barrier, surface wetting,
morphological and viscoelastic properties of the films were investigated. The addition of ZNP signifi-
cantly improved the water vapor barrier and mechanical properties of the WPI without adversely
affecting the elongation of the films. Dynamical mechanical analysis and contact angle measurements
revealed that upon addition of the nanoparticles, the fractional free volume and hydrophilicity of the
WPI films decreased. Sodium caseinate containing both hydrophilic and hydrophobic groups created an
efficient interface between the hydrophobic ZNP and hydrophilic WPI matrix, allowing for a homogeneous
distribution of nanoparticles even at very high loading levels as evidenced by the scanning
electron microscope (SEM) and atomic force microscopy (AFM) images. The WPI/ZNP nanocomposite
films can potentially become effective food packaging materials.