Scale-up of complex coacervation, a fat encapsulation technology, is not trivial since the microcapsules morphology and size are highly affected by the processing conditions. So far it has been achieved empirically (trial and error approach). The goal of this study was to produce at various scale capsules with a single-oil droplet as the core material and small enough to be below sensory threshold. The turbulence level was identified as the main scale-up) criterium and a master-curve could be, drafted showing the capsule mean diameter as function of the Reynolds number, independent of the level of production scale. From a parent emulsion with specific on droplets size (12-15 mu m), the Reynolds number had to be maintained above a critical value (15,000) to avoid capsules agglomeration with multiple on cores and large particle sizes. To avoid aggregation, this turbulence level had to be kept until the temperature dropped below a critical value (14 degrees C for a cooling rate of 35 degrees C/2 h,). Applying these learning led to a successful scale-up from bench (2 L) to a pilot plant scale of 50 L. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 1487-1496, 2009