In microwave dryers, electromagnetic energy is directly converted
to kinetic energy of water molecules. Therefore, heat is
produced within the product, and energy transfer is not affected by
transfer impediments especially in viscous materials. As microwaves
can penetrate into the material and save energy, in this
method heat can be produced in the whole volume of the material,
thereby increasing drying rate [12].
The use of vacuum in drying can be a good approach to improve
the quality of the product by facilitating moisture extraction.
Vacuum application or pressure reduction can reduce drying
temperature and therefore improve the qualitative features of food
[13,14].