The effects of whey protein isolate (WPI) were investigated on the characteristics of delactosed permeate (DLP) (moisture adsorption/desorption kinetics and glass transition temperature (T(g))) that reflect on the drying ability and shelf stability. The Peleg model showed a good fit to the moisture adsorption/desorption data for the DLP-protein samples. An increase in the protein concentration resulted in a decrease in the initial adsorption rate and adsorption capacity. However, its effect on extent of desorption in DLP-protein Mixtures was not significant. Tg increased with an increase in protein concentration. Significant relationships were observed between the Peleg constants for adsorption/desorption kinetics and Tg for the DLP-protein mixtures. (C) 2009 Elsevier Ltd. All rights reserved.