Effects of pH and the gel state on the mechanical properties, moisture contents, and glass transition temperatures of whey protein films.

The mechanical properties, moisture contents (MC), and glass transition temperature (T(g)) of whey protein isolate (WPI) films were studied at various pH values using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 degrees C and 50% relative humidity (RH) for 16 h. The critical gel concentrations (c(g)) for the cooled aqueous solutions were found to be 11.