Spray drying is the key process of the manufacturing of dairy powders. There have been a series of studies published previously on both modeling the drying characteristics of a single milk droplet and the dryer wide simulations incorporating computational fluid dynamics (CFD). In CFD simulations, it is desirable to track a large number of particles of different sizes to represent the size distribution effect. It is desirable to have an accurate yet simple model for correlating the drying rate of a single droplet, which does not require the solution of the partial differential equations. In this study, an aqueous cream and whey protein concentration solution was dried in droplet form and the appropriate reaction engineering approach (REA) model parameters obtained. The REA model predictions were compared with experimental results. Good agreement was achieved. The change of diameter of the droplet during drying was measured experimentally and compared with the model results also. The comparison between the drying characteristics of the high protein product and the high fat product reveals one aspect of compositional influence, for which the REA model has not yet been refined sufficiently to account fully. The laboratory measurements on compositional effects need to be conducted more extensively and accurately in future studies. (c) 2006 Elsevier B.V. All rights reserved.