It is reported that the similar drying conditions as subjected in the current study denature significant amount (up to 30%) of WPI (Haque et al., 2015b). Alteration of secondary structure of protein is also evident in these drying conditions. Nevertheless, the composite reaction engineering approach is still able to model the drying kinetics well. This could be because of the accuracy of the relative activation energy of protein which captures well the protein denaturation. It appears that the chemical changes during heat and mass transfer processes are incorporated in the relative activation energy (Putranto and Chen, 2015a, b). Hence, this study indicates that the composite reaction engineering approach is not only accurate to describe drying of a mixture of sugars solution (Patel et al., 2009) but also to a mixture of protein and sugar solution in which more complicated chemical changes may occur. The development of the reaction engineering approach to model drying of multiple solutes dissolved in multiple solvents (aqueous and/or non-aqueous) systems is currently underway.