Properties of and mechanisms of protein interactions in films formed from different proportions of heated and unheated whey protein solutions

A range of films were formed using different proportions of heated (80°C for 30 min) and unheated whey protein isolate (WPI) solutions. The films, with lower proportions of heated WPI solution had lower percentage elongation, tensile strength and Young's modulus, higher solubility and, in general, similar water vapour permeability, compared with a film formed from a heated WPI solution. Hydrophobic interactions and hydrogen bonding dominated in the formation of the films with lower proportions of heated WPI solution, whereas disulphide bonding played a more important role in the formation of films with higher proportions of heated WPI solution.