Milk proteins consist of casein micelles and whey proteins. Heat treatments cause denaturation of whey proteins. The denatured whey proteins may either form whey protein aggregates or may provoke whey protein coating of the casein micelles. This research focused on the effect of heat on the properties of milk proteins and their heat-induced interactions. This effect was studied in different concentrations of whey proteins and different types and concentrations of lecithins, by using three techniques; Photon Correlation Spectroscopy (PCS), Centrifugal Photosedimentometry or Centrifugal Particle Size Analyser and Differential Scanning Calorimetry (DSC). From the overall results obtained, it was concluded that the heat-induced interaction between casein micelles and whey proteins could be reduced by addition of hydrophilic lecithins, which could be due to the fact that the latter stabilises the unfolded state of the denatured whey proteins and hence minimises its aggregation and interaction with other proteins.