The purpose of this study was to produce an oil-in-water nano-emulsion by microfluidization and ultrasonication for spray drying encapsulation. Maltodextrin combined with a surface-active biopolymer (Hi-Cap) at a ratio of 3:1 were used as the continuous phase, while dispersed phase consisted Of D-limonene. Results showed that microfluidization was an efficient emulsification technique producing small emulsion droplets with narrow distributions compared with conventional emulsifying devices. The main problem was that increasing the microfluidization energy input beyond moderate pressures (40-60 MPa) and cycles (1-2) lead to "over-processing" of emulsion droplets due to re-coalescence. In general, it was not possible to decrease emulsion droplet size below 0.5 mu m by microfluidizer. For ultrasound emulsification, increasing the energy input through improving sonication time helped to reduce emulsion size with minimum recoalescence of new droplets, but the results were depending on the coarse emulsion preparation method. (C) 2007 Elsevier Ltd. All rights reserved.