The effect of pH and mechanical processes on non-heated whey protein isolate (WPI) and WPI fibril was evaluated from structural, physical and emulsifying properties. Fibril aggregation was observed increasing pH from 2 to 7 whilst mechanical processes with high energy density resulted in fibril shortening and smaller aggregates. Despite affecting fibril morphology, mechanical processes did not affect significantly the protein secondary structure conformation and interfacial tension at aqueous protein dispersion-oil interface. However, increasing pH resulted in loss of ordered secondary structure, decreased interfacial tension and surface hydrophobicity of fibril. Fibril dispersions showed shear thinning behavior but thixotropy was only observed at pH 7. Fibril-stabilized emulsions at pH 7 were more stable due to the higher viscosity and faster migration of fibrils to the interface when compared to fibrils at low pH, resulting in steric hindrance stabilization. Therefore, changes on WPI fibrils resulted in varied structural and emulsifying properties. (C) 2017 Elsevier Ltd. All rights reserved.