Water Vapor Permeability and Solubility of Films from Hydrolyzed Whey Protein

The effects of whey protein hydrolysis on film water vapor permeability (WVP) and solubility at 3 plasticizer levels were studied. Little or no significant difference (p > 0.05) appeared for film WVP between unhydrolyzed whey protein isolate (WPI), 5.5% degree of hydrolysis (DH) WPI and 10% DH WPI films at comparable plasticizer contents. However, increase in glycerol (gly) content significantly increased film WVP. Thus, reduction in WPI molecular weight (MW) through hydrolysis may be a better approach to improving film flexibility than addition of plasticizer. Both 5.5% and 10% DH WPI had significantly different (p ≤ 0.05) film solubility compared to unhydrolyzed WPI. Soluble Protein (SP) and total soluble matter (TSM) of hydrolyzed WPI films were much higher than for unhydrolyzed WPI films.