Oxygen Permeability and Mechanical Properties of Films from Hydrolyzed Whey Protein

The effects of whey protein hydrolysis on film oxygen permeability (OP) and mechanical properties at several glycerol-plasticizer levels were studied. Both 5.5% and 10% degree of hydrolysis (DH) whey protein isolate (WPI) had significant effect (p </= 0.05) on film tensile properties compared to unhydrolyzed WPI. Hydrolyzed WPI required less glycerol to achieve the same mechanical properties compared to those of unhydrolyzed WPI. Little or no significant difference (p > 0.05) occurred for film OP between unhydrolyzed WPI, 5.5% DH WPI, and 10% DH WPI films at the same glycerol content. Hydrolyzed WPI films of mechanical properties similar to those of WPI films had better oxygen barrier. Therefore, use of hydrolyzed WPI allowed achievement of desired film flexibility with less glycerol and with smaller increase in OP.