Spray drying is widely used to manufacture many powdered products. The drying process parameters have significant influence over the final powder’s surface properties and propensity for unwanted caking. Many factors can affect caking behavior. In most cases caking experiments are performed on bulk powders. Especially in multi-component powders it is often difficult to interpret the results, where interaction effects between particles can be complex. New techniques investigating properties at a particulate level need to be employed.

By using a combination of atomic force microscopy (AFM) based techniques, including phase imaging, force modulation microscopy (FMM) and nanoindentation, Dominic C. Prime, De Montfort University, UK, and colleagues investigated the material properties of a model milk powder system down to the nanoscale. They showed that material properties at the surface and in the particle wall are not uniform. Non-uniform material characteristics have also been shown across the particle wall.

Samples can be imaged as is, without sample coating, enabling them to be rescanned at intervals following controlled variations in humidity and/or temperature.

• Caking Behaviour of Spray-Dried Powders – Using Scanning Probe Microscopy to Study Nanoscale Surface Properties and Material Composition,
  Dominic C. Prime, Mark C. Leaper, James R. Jones, David J. Richardson, Chris D. Rielly, Andrew G. F. Stapley,
  Chem. Eng. Technol. 2011, 34.
  DOI: 10.1002/ceat.201000537