O/W emulsification capabilities of a multi-shaft stirred vessel comprising a Paravisc impeller mounted on central shaft and an off-centered rotor-stator were investigated in the case of viscous emulsions. The power consumption and the droplet size distribution were measured for different oil to water ratio using an online torque meter and a laser granulometer respectively It was found that the rotor-stator had a reduced effect on the processing time and the droplet size distribution and that the presence of the Paravisc significantly influenced the processing time, overall energy consumption and the shape of the droplet size distribution. The study also highlighted the significant influence of the oil internal phase to water ratio on the processing and structural parameters of the emulsion. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.