A comparison of the emulsification performance of a high-pressure valve homogeniser (HPH) and a Microfluidizer has been carried out for a range of different oil to aqueous phase viscosity ratios, emulsifier types, pressure drops and number of passes through the chambers. It has been shown that for the same pressure drop across the two chambers, similar droplet sizes are produced (after 5 passes). Differences in droplet size were observed after a single pass, with the HPH producing larger droplets with a wider distribution of sizes. This difference can be attributed to the design of the homogenisation chambers with the HPH producing a wide distribution of shearing forces, so all of the starting emulsion does not experience the maximum stresses at each pass. Droplet size has been shown to be independent of viscosity ratio (0.1-80) for both homogenisers indicating that breakup is occurring in turbulent flow. No effect of emulsifier was observed in the Microfluidizer with SDS, Tween 20 and sodium caseinate. However, with the HPH, the droplet size reached a limiting value after 2 passes with SDS while with Tween 20 and sodium caseinate 5 passes were required indicating that coalescence occurs in the HPH but this is more effectively eliminated by SDS. (C) 2012 Elsevier Ltd. All rights reserved.