Changes in quality properties and tissue histology of lightly salted tuna meat subjected to multiple freeze-thaw cycles.

The influence of various freeze-thaw cycles on the physicochemical and histological properties of lightly salted tuna meat was studied. Enhanced water-holding capacity and springiness were obtained in the salted samples even after repeated freezing-thawing, which was ascribed to the modifications in tissue microstructure, ice crystal morphology, and protein properties. Intracellular and spherical ice crystals were observed in the salted meat, rather than the extracellular and large ice columns in the unsalted counterparts. Proteins in the salted meat were more sensitive to the stresses imposed by freezing-thawing and would form hydrophobic interactions more readily. Excessive freeze-thaw cycles accelerated the discoloration of salted meat, probably due to the decreased oxidative stability by salt. The overall quality properties of lightly salted tuna meat could be better maintained when subjected to no more than three freeze-thaw cycles.