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30% of the world’s agricultural production is lost in post-harvest stage due to the perishability of
agricultural food items. To alleviate this problem, food can be dried to prolong its shelf life.
However, there is a trade-off between product quality and energy cost for most dehydration
methods. The objective of this study was to develop a food drying method that could deliver
product quality that was competitive with highly eco-hazardous and energy intensive methods
while being more energy efficient. To meet this objective, a solar thermal regenerated liquid
desiccant dehumidification system was designed and manufactured. It was connected to a
Microwave-Convection heating chamber to house the food items to be dried. To reduce energy
consumption even further, it was theorized that instead of operating the Desiccant-MicrowaveConvection drying process consistently, the process could be divided into three stages; starting
with high temperature Convection drying, followed by Microwave-Convection drying at a reduced
temperature, followed by Desiccant assisted Convection drying at an even lower temperature.
The Desiccant-Microwave-Convection dryer was experimentally tested to dry potato slices. The
combined process delivered 81.6% shorter drying time compared to Convective Drying and 27.8%
shorter drying time compared to Microwave Drying. The process was also found to consume
66.1%, 10% and 5% lower energy compared to Convective Drying, Microwave drying and
combined Microwave-Convection drying respectively. It was also found to retain 87.8% of the
original food’s color. When the process was divided into three stages with sequentially reducing
temperatures, the cascaded configuration resulted in 22.2% reduction in energy consumption
compared to using Desiccant-Microwave-Convection drying continuously and preserved 92.5%
of the potatoes’ original color, which is comparable to Freeze Drying.
The findings of this study are encouraging and can be used to further develop desiccant based
hybrid drying techniques for a range of food items.