LIQUID HOLDING CAPACITY AND STRUCTURAL-CHANGES DURING HEATING OF FISHMUSCLE - COD (GADUS-MORHUA L) AND SALMON (SALMO-SALAR)

The loss of water and fat in cod and salmon muscle was studied as a fu nction of heating temperature from 5-70-degrees-C. The liquid-holding capacity was measured by a low speed centrifugation net test leading t o the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the sampl es were evaluated by light microscopy. Two different preparation techn iques were used. Cod lost twice as much water as salmon upon heating. After an initial delay, the water loss increased at 20-35-degrees-C, a ttained a maximum at 45-50-degrees-C, and thereafter decreased in both fish species. Salmon muscle was more heat-stable than cod muscle. Sin ce the main structural changes appeared in the connective tissue at lo w temperatures (5-40-degrees-C), the water loss at these temperatures is probably mainly due to denaturation and melting of collagen. The ma ximum water loss was attained when the muscle cell shrank due to denat uration of myosin. The reduced water loss at higher temperatures (50-7 0-degrees-C) is probably caused by aggregates of sarcoplasmic proteins stabilizing the aqueous phase.