Plasticized whey-protein and whey-protein emulsion films were produced using sorbitol and glycerol
as plasticizers and butterfat and candelilla wax as lipids. Protein, plasticizer, and lipid ratios were
optimized to obtain acceptable free-standing flexible films. Water solubility (20 °C, 24 h) and moisture
sorption isotherms (0.18-0.90 aw, 25 °C) of the films were determined. The experimental moisture
sorption isotherm values were fitted using the Guggenheim-Anderson-DeBoer (GAB) model.
Solubility and equilibrium moisture contents (EMC) of the films were influenced by plasticizer and
lipid incorporation. EMCs of all films increased rapidly at aw g 0.65. Incorporation of lipids reduced
solubilities and EMCs of sorbitol- and glycerol-plasticized films. The effects of plasticizer and lipid
type on GAB constants were also determined.