Drying is one of the alternative methods to produce oil-free snack products. However, conventional hot air drying produces poor quality chips that have problems associated with shrinkage, dark color and hard texture. To improve the quality of the dried products and the process efficiency, microwave vacuum drying could be used (Figiel, 2009). As microwaves can penetrate deep into food material, the entire food product is heated up quickly from the inside to the outside. As a result, rapid water evaporation and the outward flux of escaping vapor are noticeable. Therefore, a possible reduction in the drying time has been suggested (Hu et al., 2006). Giri and Prasad (2007) reported a reduction of 70–90% in the drying time of mushrooms, when hot air drying was replaced with microwave vacuum drying. In addition, Therdthai and Zhou (2009) observed an increase in the drying kinetic rate constant with increased
microwave power intensity.