Dairy industries produce large quantities of effluent that commonly contain emulsified lipids. Conventional wastewater treatments are not effective when the emulsion is stable and its break may be achieved by de-emulsifier addition, like chitosan. The aim of this work was to understand the role of chitosan on de-emulsification process by the study of model emulsions that simulate a dairy waste. The emulsions (10 % (w/w) of sunflower oil and 90 % (w/w) of whey protein isolate (WPI) solution (2 %w/v) were prepared in a rotor-stator homogenizer (4 min /10,000 rpm). Afterwards, chitosan solutions (0.66 %, 0.35 % and 0.1 % w/v) were added and the pH adjusted to 6.7. A control emulsion (without chitosan) was also evaluated. Stability, morphology, flow curves (0 to 300 s-1) and frequency sweep tests (0.01 to 10 Hz) were evaluated for emulsions. After 24 h of preparation the emulsions separated in two phases: an aqueous bottom phase and an upper phase with chitosan, WPI and oil. The sample added of chitosan solution 0.1 % w/v presented the higher water separation and a smaller turbidity on aqueous phase when compared to the control The presence of chitosan and WPI lead to formation of aggregates which were broken with shearing increase. The apparent viscosity at 10 s-1 was bigger for emulsions that showed higher amounts of chitosan (5,48 and 5,51 Pa.s for 0.66 and 0.35 % respectively) comparing with those that present less amount of chitosan (0.58 and 0.59 Pa.s for 0.1 % and control respectively) suggesting a gel network formation at the interface Chitosan formed electrostatic complexes with WPI, leading an emulsion destabilization through the water separation and removal of protein from the interface.