Liquid Holding Capacity and Structural Changes During Heating of Fish Muscle: Cod (Gadus morhua L.) and Salmon (Salmo salar)

The loss of water and fat in cod and salmon muscle was studied as a function of heating temperature from 5-7o•c. The liquid-holding capacity was measured by a low speed centrifugation net test leading to the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the samples were evaluated by light microscopy. Two different preparation techniques were used . Cod lost twice as much water as salmon upon beating. After an initial delay , the water loss increased at 20-35°C, attained a maximum at 45-50°C, and thereafter decreased in both fish species. Salmon muscle was more heat-stable than cod muscle. Since the main structural changes appeared in the connective tissue at low temperatures (5-40°C), the water loss at these temperatures is probably mainly due to denaturation and melting of collagen. The maximum water loss was attained when the muscle cell shrank due to denaturation of myosin. The reduced water loss at higher temperatures (50-70°C) is probably caused by aggregates of sarcoplasmic proteins stabilizing the aqueous phase.