Dehydration and rehydration characteristics of pretreated pumpkin slices

The influence of an alternative chemical pretreatment on dehydration and rehydration of an Italian ecotype pumpkin was investigated. The pretreatment consisted of soaking the slices in a diluted solution of trehalose, sucrose and NaCl. Hot air-drying was performed in a convective dryer at temperatures of 55, 60, 65 and 70°C. Samples treated prior to drying showed a shorter (about 1/4) drying time, less volume shrinkage and colour changes, but showed higher rehydration capacity compared to untreated ones, especially in the range 55-65°C. Moreover, the pretreatment was effective in retention of total phenolic content and antioxidant activity. The Midilli model was the most appropriate for describing drying behaviour, while the Weibull model for rehydration.