Histological Characteristics of Grass Carp Muscle during Cold Storage
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Abstract:
The histological features and changes in lipid and protein characteristics of grass carp muscle during cold storage at 2 ℃~4 ℃ were investigated using transmission electron microscopy, gas chromatography-mass spectrophotometry, and sodium dodecyl sulfate- polyacrylamide gel electrophoresis. The results showed that there was a large number of lipid droplets accumulated below the sarcolemma of fresh grass carp muscle and most of these droplets showed signs of discharging. Additionally, there were numerouslipid droplets with diameter of 0.25~0.5 μm around the mitochondria, observed between myofibrils in the abdominal muscle of the fish. However, no lipid droplets were found between the myofibrils in the muscle of the back region. During cold storage at 2 ℃~4 ℃, varying degrees of rupture were observed in the myofilaments of grass carp muscle, and the cell structure gradually disintegrated. In severe cases, autolysis or watery transformation appeared in a large area of myofibrils; vacuole-like cells and degenerated cell debris were noted; severe edema accumulated in sarcoplasmic reticulum and mitochondrias; intracellular lipid droplets gradually migrated toward the sarcolemma, where they slowly degraded. Meanwhile, with increasing cold storage time, monounsaturated fatty acids, polyunsaturated fatty acids, and their main corresponding fatty acids degraded gradually, while saturated fatty acids and their main corresponding fatty acids increased. Furthermore, myofibrillar content and sarcoplasmic proteins gradually degraded. The significant degradation of myosin heavy chains and actin led to a gradual rupture of myofilament in the muscle and visual blurring of cell structures, which eventually led to deterioration of fish meat quality.
