The efficiency of conventional flotation sharply reduces when the diameter of dispersed particles are less than 10 mum and it fails completely for particles less than 1 mum. Colloidal gas aphron (CGA) bubbles, offer particular advantages in the removal of ultra-fine particles. Aphron flotation can be considered for separation of whey protein because of its submicron size. As the characteristics of aphron bubbles play a key role on the performance of flotation, the experiments conducted in this work were specially designed to test the effect of gas transfer during aphron generation process. This has been done by investigating the effect of the spinning disc position in aphron generator and also the mode of surfactant addition on aphron flotation of whey protein at two different temperatures. It was found that gas transfer into dispersion during aphron generation is a controlling step for aphron flotation. (C) 2003 Elsevier B.V. All rights reserved.