Drying of Tomato Using Different Methods: Comparison of Dehydration and Rehydration Kinetics

Drying of tomato slices was carried out using five different methods, viz., hot air (HAD), solar cabinet (SCD), heat pump (HPD), microwave vacuum (MVD), and freeze drying (FD). During drying by hot air, solar cabinet, and heat pump drying only falling rate periods were observed, whereas microwave vacuum and freeze-drying processes showed both the constant and falling rate periods. The Page model constant, moisture diffusivity, and Peleg model constants were estimated to compare the dehydration and rehydration kinetics. During microwave vacuum drying of tomato the highest values of Page model rate constant and moisture diffusivity were obtained, whereas freeze drying resulted in lowest values. During rehydration studies, heat pump and microwave vacuum-dried tomato slices showed comparatively higher rehydration ratios than hot air- and solar cabinet-dried slices, whereas freeze-dried samples showed the highest rehydration ratio. Also, Peleg model constants were estimated.