Effect of molecular interactions in whey protein isolate based films and coatings on their thermoformability
Whey protein is a particularly well studied and a promising raw material to enhance functionalities, such as oxygen barrier, of food packaging materials. Several publications as well as work conducted by the authors reveal that the packaging relevant techno-functional properties depend on numerous factors. These are among others for instance storage time, average molecular weight, degree of protein denaturation and exposure to UV-radiation. These factors influence both, mechanical as well as barrier properties. However, so far it is still not well understood, how the above mentioned factors affect the protein network on a molecular level in whey protein isolate (WPI) based films and how this affects the further processing and properties of suchlike materials. This study aimed on determining the impact of molecular interactions in WPI based films on their mechanical properties, in particular their thermoformability. Therefore the protein-protein interactions were specifically influenced by certain additives. The impact of this treatment on covalent and non-covalent intermolecular interactions in protein films and coatings was determined by protein solubility studies using specific buffer systems combined with a Bradford assay. Furthermore the films were characterized regarding their mechanical and barrier properties. By this approach a correlation between protein-protein interactions on a molecular level and application relevant properties such as elongation at break could be derived. This allows to adjust certain mechanical characteristics of protein based films and coatings such as their thermoformability. Hence this study provides new results for researchers and material developers to better understand the molecular interaction-property relationships of WPI based films and coatings.