The in¯uence of the composition and structure of oil-in-water emulsions on aroma retention was examined for 20 volatile compounds. Compositional and structural parameters included the fraction of emulsi®er phase, the fraction of lipid phase and the particle size distribution of the dispersed lipid phase in the emulsion. Air/liquid partition coef®cients of dimethyl sulphide, 1-propanol, diacetyl, 2-butanone, ethyl acetate, 1-butanol, 2-pentanol, propyl acetate, 3-methyl-1-butanol, ethyl butyrate, hexanal, butyl acetate, 1-hexanol, 2-heptanone, heptanal, a-pinene, 2-octanone, octanal, 2-nonanol and 2-decanone were determined by static headspace gas chromatography. The hydrophobicity of the compounds determined the in¯uence of the compositional and structural parameters of the emulsions on air/liquid partitioning. Increase of the emulsi®er fraction increased the retention of mainly hydrophilic aroma compounds and decreased the retention of hydrophobic compounds. Higher lipid levels led to increased retention of hydrophobic compounds and release of hydrophilic compounds. Emulsions with larger particles showed increased aroma retention, which was independent of the lipid fraction and the polarity of the aroma compounds. The data demonstrated a profound effect of both composition and structure of oil-in-water emulsions on the air/liquid partitioning of the 20 aroma compounds under equilibrium conditions.