2.5. Freeze-drying
The dipped and undipped frozen samples with 20% and
40% weight reductions achieved with IR heating and the control
samples were removed from the freezer after they were
completely frozen and then placed in a pilot scale freeze dryer
(VirTis UltraVirTual Series EL unit). The freeze dryer was
operated in shelf driven mode, which was controlled based
on shelf temperature, and run with programmed procedures.
In order to determine the drying characteristics of the banana
slices during freeze-drying, the samples were dried for
various times of up to 40 h. The samples were weighed at
the end of each time period and the moisture content was calculated
and reported. The samples with moisture content
higher than 5 g moisture/100 g wet weight were further dried
to obtain a similar moisture content for all samples used for
quality evaluation.