The objective of this study was to investigate quality changes of salmon fillet muscle during thermal sterilization processes. Small samples (D 30 mm x H 6 mm) from the central dorsal region were heated in an oil bath at 121.1 degrees C for periods varying from 5 to 120 min. The quality variations along the longitudinal axis of salmon fillets (raw and heated) were examined. The quality properties studied included shear force, color, cook loss, and shrinkage. To minimize the influence of the heterogeneity of the salmon muscle, a multiple thin blade texture device was developed for shear force measurement and a computer vision system was used to facilitate accurate measurements of color and shrinkage. The red muscle was firmer than the white muscle in the raw but not in heated samples. Muscle from the central dorsal region had a lower cook loss and less shrinkage than samples from either the anterior or posterior region following heating. The greatest change in quality occurred within the 1st 10 min of heating at 121.1 degrees C. Shear force measurements following heating indicated 2 peaks, one corresponding to 5 min and the second for 60 min processing at 121.1 degrees C. Possible mechanisms were discussed.