Effect of Pulsed Light treatment on the functional properties of casein films

In this study, the effect of Pulsed Light (PL) treatment as a cross-linking method on the properties of casein films was evaluated. Casein films were prepared from micellar casein concentrate, with 5 g/100 g glycerol added as a plasticizer. The UV-curable resins PEG (200) diacrylate and PEG (400) diacrylate were added as photo-initiators. Films were prepared by casting and equilibrated under a range of relative humidity (%RH), then treated with Pulsed Light (PL), with up to 15 pulses of light on each side, at a fluence of 1.57 J/cm(2) per pulse. The microstructure, mechanical and water barrier properties, water sorption and hydrophobicity of the films were evaluated. PL treatment of casein films with up to 12 pulses increased the films' smoothness and homogeneity, while higher levels of treatment caused structural defects. Mechanical strength and elongation of some of the films, particularly those with added PEG (400) diacrylate, were significantly increased by PL, but no improvement of their water vapor permeability was observed. The incorporation of PEG (200) diacrylate resulted in highly porous film microstructures, and interesting photo-patterning effects observed at high PL doses. These results indicate the potential of PL for creating protein films with unique characteristics and functionality. (C) 2015 Elsevier Ltd. All rights reserved.