Effect of thermal treatment on moisture transport during steam cooking of skipjack tuna (Katsuwonas pelamis)

Moisture and mass loss were determined during atmospheric steam cooking of skipjack tuna by measurement of muscle moisture content in whole fish and on-line measurement of mass and temperature in fillets. Thermal denaturation temperatures of muscle proteins were measured by differential scanning calorimetry. Muscle moisture content and mass loss were dependent on muscle temperature. Temperature distribution was predicted and mass loss rates were calculated in fillets. A decreasing rate of mass loss was followed by a steady rate period and a resumption of a decreasing rate period. The increased loss of mass during the steady period corresponded to thermal denaturation temperatures of muscle proteins. Changes in mass loss rates resulted from a gradient of muscle changes produced by the temperature gradient created during cooking.