Hot water treatment at 45 C/25 min of whole kiwifruit
is an effective methodology in quality maintenance of fruit
slices, increasing fruit firmness and avoiding an excessive
softening. The presence of calcium in dip solutions during
heat treatment had a marginal effect in fruit firmness. Dip
treatment leads to partial calcium loss from the fruit, this
effect being minimized when treatment was conducted in
3% CaCl2 solution. PME is activated by heat treatment
but in the presence of calcium this effect is reduced or even
inhibited. Therefore, it is tentatively concluded that firmness
preservation is due to PME activation, though the
degree of methylesterification of pectin for the different
samples might permit a definite conclusion. No HSP in
the range of 94–14.4 kDa were detected as a consequence
of the applied treatments which leads us to think that these
proteins were not involved in quality maintenance of kiwifruit
slices. Although calcium presence did not induce benefits
on the quality preservation of fruit slices, it also did
not cause negative effects when present in the heat treatment
solution.