The gelation characteristics of myofibrillar proteins are indicative of the ultimate texture of fish products. This study investigated the impact of pH (5.6-7.0) on viscoelastic properties of tuna myofibrillar proteins using dynamic oscillatory rheometer under both small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS). Using small-strain oscillatory tests, the rheological properties during gelling were quantified. Results indicated that protein denaturation and gel formation were pH dependent. LAOS tests indicated that pH strongly affected the structure of the myofibrillar proteins system as shown by deformation of the nonlinear stress response curve. Increasing pH produced an increasingly strong, more stable network. All non-linear behaviors increased with increasing strain in a similar manner, suggesting a general mechanism responsible for strain effects that was similar for non-linear and fracture behavior. Furthermore, pH also appeared to influence the water-holding capacity and surface hydrophobicity. (C) 2013 Elsevier Ltd. All rights reserved.