The penetration depth of microwaves at 2.45 GHz is limited for large scale drying whereas radio frequency (RF) heating at 10–300 MHz can give better penetration depth. In some cases, rapid mass transport might cause change in the food texture called ‘puffing’ which might be desirable or undesirable depending on the final product (Zhang et al., 2006). Hence it is necessary to combine microwave drying with conventional drying in order to enhance drying rate as well as maintain product quality.