Microwave drying of sweet potato: drying kinetics and energetic analysis.

Abstract

The shelf life of the sweet potato is short due to its high water activity. Therefore, preservative techniques are mandatory. In this sense, the effects of osmotic dehydration (OD) as pretreatment, two different osmotic agents (OA), sucrose and sorbitol, and microwave power density (PD) on the drying kinetics of sweet potato slices (SPS) were studied. The SPS were immersed (pretreated) or not (untreated) in an osmotic solution at aw = 0.900. The samples were placed in the microwave and the drying proceeded until the moisture content was 0.20 ± 0.02 kg water/kg. The results showed that drying time, effective diffusivity, and specific energy consumption (SEC) increased with both increasing the microwave PD and employing OD. The effective diffusivity and SEC ranged from 5.701 × 10-10 to 5.218 × 10-9 m 2 /s and from 7.702 MJ/kgwater to 15.608 MJ/kgwater, respectively. An adapted model was achieved for describing the drying behavior and presented suitable adjustments. According to the results, 10W/g-sucrose must be selected for drying SPS. Drying time, SEC and η at this level were 480 s, 7.702 MJ/kgwater and 29.30%, respectively.