BACKGROUND: Supercritical antisolvent (SAS) micronisation of synthetic trans-beta-carotene was studied using tetrahydrofuran (THF) as solvent and supercritical carbon dioxide (CO2) as antisolvent, with the objective of increasing its bioavailability and facilitating its dispersion in oil and emulsion formulations as a result of its smaller particle size. The micronised powder was analysed by scanning electron microscopy and high-performance liquid chromatography. Micronisation experiments were performed in order to evaluate the effects of temperature (308.15-333.15 K), pressure (6.5-13 MPa) and concentration of the liquid solution (6-9 g L-1). The effect of the supercritical CO2/THF flow ratio in the range between 4 and 44 (on a mass basis) was also analysed. Determinations of equilibrium concentrations of beta-carotene in the CO2/THF mixture were also performed. RESULTS: The particle size obtained ranged from 1 to 500 mu m, with mean particle diameters around 100 gm. Three types of morphology were found in the precipitated powder: crystalline with superficial pores and leaf-like appearance; crystalline with regular shapes and blade-like edges; and crystalline without superficial pores and leaf-like apearance. The Peng-Robinson equation of state was used to calculate the density of the CO2/THF binary mixture, and the solubility of beta-carotene in this mixture was correlated with its density. CONCLUSION: The use of the SAS technique to micronise beta-carotene proved to be efficient, and the absence of degradation in the micronised powder allows the industrial application of this technique. (C) 2008 Society of Chemical Industry