Liquid Loss as Effected by Post mortem Ultrastructural Changes in Fish Muscle: Cod (Gadus morhua L and Salmon Salmo salar

Abstract

Abstract:This study was performed in order to assess the effect of early post mortem structural changes in the muscle upon the liquid-holding capacity of wild cod, net-pen-fed cod (fed cod) and farmed salmon. The liquid-holding capacity was measured by a low speed centrifugation test. Transmission electron microscopy was used to discover ultrastructural changes both in the connective tissue and in the myofibrils. Differential scanning calorimetric thermograms of the muscle proteins were recorded to elucidate whether fundamental differences did exist between the proteins of the raw material tested. Multivariate statistics were used to explicate the main tendencies of variations in the thermograms. The salmon muscle possessed much better liquid-holding properties than the cod muscle, and wild cod better than fed cod regardless of the storage time. Both fed cod and farmed salmon, underwent the most severe structural alterations, probably caused by the low muscle pH values. The higher liquid-holding capacity of the salmon muscle was related to species specific structural features and better stability of the muscle proteins. The myofibrils of the salmon muscle were denser and intr.a-and extracellular spaces were filled by fat and a granulated material. The differences in thermograms of muscle from wild and fed cod were largely explained by the variations in pH. The severe liquid loss of fed cod is due to a low pH induced denaturation and shrinkage of the myofibrils. Post mortem degradation of the endomysial layer and the sarcolemma may have further facilitated the: release of liquid.

Degradation of myofibrils in cultured yellowtail Seriola quinqueradiata burnt meat: effects of a myofibril-bound EDTA-sensitive protease

“…The lower muscle pH can lead to negative effects (such as poor liquid-holding capacity and a rapid degradation of the muscle proteins) on the quality of fish according to several reports [17,25,26]. During the culture of some fishes, intensive feeding increased the glycogen level in the muscle [17,25,26]. Post-mortem, high muscle temperature caused rapid glycolysis, which increased the lactic acid content and consequently caused the drop in pH [1,27].…”

Effect of Season, Location, Filleting Regime and Storage on Water Holding Properties of Farmed Atlantic Salmon (Salmo salar L.)

“…The WHC is also known to be affected by pH, because pH close to the isoelectric point is known to lower the WHC (4). The drip loss from salmon fillets consist mainly of water, proteins and lipids and is affected by a drop in muscle pH due to anaerobic glycolysis (9) and ultra-structural changes during rigor mortis (10). A rapid drop of pH can in all likelihood, also lead to denaturation of muscle and sarcoplasmic proteins.…”

“…WHC of Atlantic salmon is known to be affected by several pre-and post mortem factors included stress prior to slaughtering (6,7), starvation (8), and state of rigor mortis (9,10). The WHC is also known to be affected by pH, because pH close to the isoelectric point is known to lower the WHC (4).…”

Changes in Texture and Liquid Holding Capacity of Spiced Liquid Smoked Silver Carp (Hypophthalmichthys Molitrix) Muscle Wrapped in Aluminium Foil during Refrigerated Storage

“…This is important economically since fish is sold by weight. The content of water and its distribution within the flesh also affects the quality [19]. The `free' water, amounts to about 90% of the tissue water, is held by capillary and surface tension forces mainly in intracellular locations.…”