Rapeseed protein isolate has promising functional properties (e.g. emulsifying and foaming), but is often extracted with intensive purification steps. This requires a considerable use of resources and damages protein functionality regarding, for instance, foam stabilization. We studied the interfacial and foaming properties of a mildly obtained rapeseed protein concentrate that contained oleosomes, and of its derived defatted rapeseed protein concentrate after solvent-based defatting. The air-water interfaces were deformed with large amplitude dilatational and shear deformations, which were analysed with Lissajous plots. At low bulk concentrations (0.01% w/w), the rapeseed protein-stabilised interfaces behaved as viscoelastic solids. The interfacial films became weaker and more stretchable at higher concentrations, suggesting that more non-protein components interfere with the intermolecular interactions between the adsorbed proteins at higher bulk concentrations. We confirmed the presence of such non-protein components at the interface by analysing Langmuir-Blodgett films with atomic force microscopy. The stability and air bubble size of foams prepared with either rapeseed protein concentrate or defatted rapeseed protein concentrate were similar. Mild purification of rapeseed resulted in a protein concentrate containing lipids in their native oleosome form, which have a minor destabilizing effect on foams. We conclude that mild purification is a suitable method to obtain sustainably produced protein concentrates with promising foaming properties.