Drying techniques Drying is a mass transfer process of removing
moisture from food products to reduce the bulkiness of agricultural
produce (Gatea, 2011; Radhika et al., 2011). Drying involves heat
transfer, therefore, reducing energy consumption, improving the drying
process efficiency and obtaining high quality products with minimal
costs will be the goal of modern drying (Doymaz, 2011; Darvishi et al.,
2014). Convective hot air drying of agricultural produce is the most
common method used to remove moisture from food products. However,
the shortcomings of this method include slow and long drying period,
high energy consumption and contamination of food products as a result
of poor handling, low energy efficiency (Sarimeseli, 2011). However, in
order to reduce the problems and to achieve a more effective and faster
thermal drying process, the use of microwave and dielectric heating
methods for drying agricultural produce is encouraged (Sarimeseli,
2011). Microwave and dielectric heating methods are characterized by
higher drying rate, shorter drying time, decreased energy consumption
and better quality dried products which make them more preferred than
the convective hot air drying (Sarimeseli, 2011). Drying methods are
broadly divided into two namely, natural and artificial drying methods.
The natural drying method uses the solar energy to remove moisture
from food products. This method depends on variability of weather
conditions which makes it highly unreliable (Toshniwal and Karale, 2013).
On the other hand, artificial drying method is more preferred than
natural method of drying because of faster drying rate and efficiency
and effectiveness in removing large amount of moisture from produce
which result into better quality dried products (Toshniwal and Karale,
2013). In addition, there is better control of various factors involved in
the drying process such as temperature, drying air flux and time of
drying. In artificial drying effectiveness and efficiency of drying operation
could be improved through the use of mechanical or electrical
equipment such as fans.
