This difference may be related to the changes in the amount,
distribution and mobility of unfrozen water in the stem lettuce
cubes due to blanching. Unfrozen water has a major impact on
the ionic mobility in the frozen samples. Electrical conductivities
of all three samples declined with decreasing temperature in cooling
stage because of the decrease in the ionic mobility. After the
samples temperature was below zero all freezable water molecules
in the samples were gradually frozen to solid state. There were
only small amounts of un-freezable water and bound water in the samples. Since there were no ions and soluble solutes lost in
the MWB samples (Ramesh et al., 2002; Lin and Brewer, 2005), unlike
in HWB samples, large amounts of un-freezable water and
higher mobility occurred in the frozen MWB samples leading to
the lowest transition temperatures. NOB samples had lower transition
temperature than HWB probably because of loss of soluble
solutes during HWB.