Mean protein dispersion density ranged from 1003.7 to 1006.0 kg/m3 and increased with increasing temperature due to molecular mass distribution (Fig. 3c). Variation of density at each temperature was quite high and this may be assigned to high polydispersity of the samples. Densities of the samples heated at 60 and 70 °C were comparable. No significant difference was found in densities of dispersions heated at 90 and 95 °C, what may suggest some limitations in a molecular mass increase of agglomerates at higher temperatures of protein preheating. Most changes in the molecular mass of aggregates, formed under heating, took part around denaturation temperature of whey proteins, i.e. 75–80 °C (Millqvist-Fureby et al., 2001). Fig. 3d presents results of emulsifying capacity measurements. Less oil was emulsified by unheated samples (122.3 ml), comparing to these heated at 60 °C (205.4 ml). At the temperature of 60 °C probably the first sign of denaturation, protein unfolding, favoured emulsification.