The TOF for the interface movement
(TOFunfrozen), i.e. the difference between echoes 2 and 3,
showed a similar dependence on time decreasing from
an initial value equivalent to TOFtotal (no ice present) to
zero (no unfrozen product present). Similar results were
obtained for freezing of both chicken breast muscle (Fig.
7a), and beef round roast (Fig. 8a). However in the
muscle foods the ice front could only be measured over a
portion of the freezing process. At the very early stages,
the echo could not be resolved from the back wall reflection
while at latter stages the echo became too small
to be distinguished from baseline noise.