Quality and structural changes in starchy foods during microwave and convective drying

This study was conducted to evaluate the quality and structural changes in potatoes during microwave and convective drying. A modified microwave oven, operated in either the microwave or convective drying mode, was used to dry the samples. The quality attributes of the dehydrated potato samples were investigated on the basis of the ascorbic acid retention (vitamin C) and rehydratibility, and the structure in terms of the shrinkage behaviour. Ascorbic acid is an important indicator of quality and its selection was due to its heat labile nature. Ascorbic acid deterioration demonstrated first-order kinetic behaviour, and was further found to depend on air temperature, microwave power and moisture content. Reduced vitamin C destruction was found in the microwave dried samples. The volumetric shrinkage of the samples exhibited a linear relation with moisture content. With convective processing, the samples exhibited uniform shrinkage throughout, however, with microwave drying two shrinkage periods were observed. Microwave dried samples had higher rehydration potential. (C) 2004 Elsevier Ltd. All rights reserved.