Structural and ultrastructural changes of full-cycle cultured Pacific bluefin tuna (Thunnus orientalis) muscle slices during chilled storage.
BACKGROUND
This study examined the structural and ultrastructural changes of dorsal and ventral muscle tissues of full-cycle cultured Pacific bluefin tuna (PBT), Thunnus orientalis Temminck & Schlegel 1844, cut into slices simulating sashimi and placed in chilled storage for varying periods. Structural and ultrastructural changes were determined in order to understand the physical texture by breaking strength measurement.


RESULTS
Progressive deterioration of myofibril structure was observed during chilled storage (4 °C) of PBT muscle slices over 5 days post mortem. Muscle degradation included detachment between myofibres, detachment of the plasmalemma, disruption of mitochondria, loss of Z-line density and alignment, cementation of myofibrils, loss of the hexagonal arrangement of thick versus thin myofilaments and migration of subsarcolemmal nuclei to intermyofibrillar spaces.


CONCLUSIONS
Loss of myofibre-myofibre adhesion, detachment of the plasmalemma and disruption of other components did not lower the breaking strength of PBT muscle. This provides evidence that the muscle breaking strength of PBT is not only associated with the detachment of myofibres or detachment of the plasmalemma. Other factors that produce cement-like substances, such as cementation of the myofibrillar components and degradation of the sarcoplasmic reticulum, may also increase breaking strength.
Laboratory of Aquatic Food Science, Department of Fisheries, Faculty of Agriculture, Kinki University, Nara 631-8505, Japan. bcroy11@yahoo.com
Bimol Chandra
BC
Roy
Masashi
M
Ando
Tomohiro
T
Itoh
Yasuyuki
Y
Tsukamasa
D000818:Animals; D017756:Aquaculture; D002462:Cell Membrane / Q000648:ultrastructure; D003080:Cold Temperature; D061353:Food Storage / Q000379:methods*; D006801:Humans; D008928:Mitochondria / Q000648:ultrastructure; D009210:Myofibrils / Q000648:ultrastructure*; D011180:Postmortem Changes; D012034:Refrigeration; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure; D017747:Seafood / Q000032:analysis*; D014413:Tuna / Q000033:anatomy & histology / Q000502:physiology*