Gamma-irradiation influence on the structure and properties of calcium caseinate-whey protein isolate based films. Part 1. Radiation effect on the structure of proteins gels and films.

Brookfield viscosimetry, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and measurements of the texture strength of gels formed with CaCl2 and the mechanical and barrier properties of the film were applied in studies of gel formation and structural and mechanical properties of gels and films prepared using calcium caseinate (CC)-whey protein isolate (WPI)-glycerol (1:1:1), control, and irradiated with 60Co gamma rays using a 32 kGy dose. The irradiated gels have appeared to be more "fine-stranded" as compared to the more "particulate" control gels and lead to the formation of more rigid films with improved mechanical strength and barrier properties. This results from cross-linking and the modification of protein conformations were induced by irradiation, in particular the increase in the beta-sheet and beta-strand contents. Structural modifications taking place in CC-WPI composition are related to modifications taking place separately in CC and WPI. Improvement of the properties of the films after irradiation corresponds to the increased density of the cross-linked material because no change in the porosity of the films was observed by TEM.