As mechanically induced processing effects on powdered materials are primarily manifested in small regions on the particle surface, they frequently remain undetected by routine chemical and physical measurement techniques. Inverse gas chromatography was employed in this study to characterize the surface properties of alpha -lactose monohydrate and determine any changes induced by milling and blending. Results highlighted the potential of this technique to detect and quantify surface energy differences induced by milling and blending and demonstrated how a second unit operation often achieves its effects by means of disrupting flaws caused during the first process. Studies of the flow properties revealed how the bulk behavior of powdered materials can change depending upon processing history, further emphasizing the importance of surface characterization in understanding the behavior of powdered materials.