Conclusion
Chitosan and whey protein films showed good potential to be
used as film forming matrices. Results obtained in this study
indicate the possibility of production of transparent WP/CS
bilayer films with higher water vapour barrier efficiency and
enhanced mechanical resistance. Thus, potential industrial
applications can be envisaged. On a microscopic level, good
adhesion and integrity of the CS and the WP layer were
observed. In all bilayer films, the air CS side was characterized
by swelling, while on the support WP sides, the films swelled
after initial absorption. Blend films followed an anomalous
behaviour that was characterized by the initial absorption and
delayed swelling. During the exposure to water vapours, water
vapour plasticized the WP and CS films. Bilayer films had
significantly lower water vapour permeability in comparison
to both pure and blend films because it was affected by
permeability of each layer. In the dry state, blend film proved
to be the best barrier to oxygen followed in respective order by
WP films, CS films and bilayer films. Lamination of WP and CS
polymer is shown to be one of the most useful methods to
obtain new materials with desired functional properties. The
bilayer CS/WP films may have useful applications in the food
systems where edible films should dissolve during the cooking
or consumption process. In addition, these films would also
have useful antimicrobial properties due to the presence of
chitosan. However, further application studies are needed and
envisaged.