Systematic experimental study of the physico-chemical factors controlling the foaming and defoaming performance of several Pluronic nonionic block copolymers is performed in solutions of sodium caseinate. Dynamic light scattering measurements and microscopic observations confirm that a significant defoaming is observed above the cloud point of the nonionics, which is almost independent on the polymer structure. However significant differences are observed in the foaming below the cloud point, which do correlate with the polymer structure. Dynamic surface tension measurements allow more detailed analysis of the mechanism of polymer and protein adsorption, and of the role of the individual components for the overall stabilization or destabilization of the foams.