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.
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Abbreviations
- △E :
-
Color change (dimensionless)
- L*:
-
Lightness (CIELab tristimulus color values)
- a*:
-
Redness (CIELab tristimulus color values)
- b*:
-
Yellowness (CIELab tristimulus color values)
- X t :
-
The content of moisture at t time on dry basis (in grams per gram dry basis)
- m t :
-
The weight of material at t (in grams)
- m d :
-
The dry matter weight of the material (in grams)
- ε′:
-
Dielectric constant
- ε′′:
-
Loss factor
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Acknowledgments
The authors express their appreciation to Frito-Lay Inc., Plano, Texas, for the financial support of this study. Discussions with Dr. Ted Farrington were very valuable during the course of this work. His support and contribution is gratefully acknowledged. The authors also thank 863-HI-TECH Research and Development Program of China for supporting the research under the contract no. 2011AA100802.
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Jiang, H., Zhang, M., Mujumdar, A.S. et al. Analysis of Temperature Distribution and SEM Images of Microwave Freeze Drying Banana Chips. Food Bioprocess Technol 6, 1144–1152 (2013). https://doi.org/10.1007/s11947-012-0801-1
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DOI: https://doi.org/10.1007/s11947-012-0801-1