Properties of Dark and Light Tissue from Horse Mackerel (Trachurus murphyi)

Mechanical and physical properties of light and dark tissues from horse mackerel (Trachurus murphyi) were determined for tissue separation. Raw dark tissue was 1.8 times harder than raw white (1.4 and 0.79 kg-f/g, respectively). Hardness after heating to 20°C decreased slightly but it increased sharply to a value of about 2.4 kg-f/ g at 40°C. Tensile strength of the skin was highest at 30°C and a large reduction in the shearing force of the interfibrillar matrix (connective tissue) was also attained at that temperature. Pieces of light muscle were denser (d =1.082) than those of dark tissue (d = 1.059) and relative separation was attained based on terminal velocities. Heating at 30°C appeared adequate to implement future mechanical disruption processes.