Modeling the effect of glycerol on the moisture sorption behavior of whey protein edible films Original Research Article

Moisture sorption isotherms (aw=0.115–0.94) were measured for a series of whey protein isolate (WPI) edible films prepared with different amounts of glycerol as a plasticizer (glycerol:total non-volatile material G=0–0.5) and for native WPI. The moisture sorption characteristics of the native protein were similar to those of the G=0 films and the equilibrium moisture content of the films increased linearly with G at all humidities. The Guggenheim-Anderson-de Boer was superior to either the Peleg or BET model as a model for the measured isotherms. The equilibrium moisture content of the films, M, was modeled using a four-parameter empirical model, M=k1 exp (k2aw)+k3 exp (k4aw)G, where k1–4 are 0.0016, 2.72, 0.0046, and 6.24, respectively (r=0.98).