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.