Analysis of Temperature Distribution and SEM Images of Microwave Freeze Drying Banana Chips

Abstract

Compared with freeze drying (FD), microwave freeze drying (MFD) using microwave as the heating source can accelerate the drying rate of bananas. This paper presents the results of an experimental study of temperature distribution during the process of MFD banana chips. The results show that the temperature distribution is uniform during the sublimation drying stage, but not at the start of the desorption stage of drying; this phase is prone to generate hot spots, which are brought about by the localized melting of ice crystals not removed in the sublimation stage and the absorption of excess microwave by sorbed water. Comparison of scanning electron microscope micrographs of FD and MFD samples shows that the major dissimilarity between the two samples is in their pore sizes. © 2012 Springer Science+Business Media, LLC.