The microstructure of full-fat mayonnaise was characterised at different structural levels by using confocal laser scanning microscopy, CLSM, and transmission electron microscopy on freeze-etched samples. The size of droplets varied, and in 80% mayonnaise many very small droplets were found between larger droplets. The colloidal structural parameters were quantified on CLSM images. A stereological approach was used to estimate the droplet size, the interfacial surface area between the fat phase and water phase, and the size of the egg yolk aggregates. The mayonnaise samples were produced by a cold process line in a pilot plant equipment. A two-level fully factorial experimental design was used, with the processing parameters, (speed of the emulsification cylinder, the speed of the visco-rotor and the out-temperature) as design variables. The results showed that the speed of the emulsification cylinder had a main effect on the size of the droplets. No other effects were found when the speed of the emulsification cylinder was high. When the speed was slow, however, an interaction effect was found on the size of the droplets. The distribution of egg yolk was affected by the processing conditions and by the quality of the egg yolk. The storage modulus G? had higher values when the mayonnaise was formed of smaller droplets at a high emulsification cylinder speed. Lower values of G? were found when the mayonnaise was formed of larger droplets produced by a slower emulsification cylinder speed. © 1999 Elsevier Science Ltd.