Assessment of some physical properties of dried potatoes

Abstract

The effect of drying behaviour on the drying rate and quality characteristics of potato slices in a vacuum-infrared drying system was studied. In this research, the effect of the infrared radiation powers (100, 150, and 200 W) and vacuum levels (20, 80, 140 mmHg and atmosphere pressure) at different slice thickness (1, 2 and 3 mm) on drying rate and shrinkage percentage and rehydration capacity were investigated.  It was concluded that infrared radiation power amount has a significant effect on processing time and drying rate. With increasing radiation power, drying time is reduced and consequently drying rate is increased. The drying rate curve of potato slices at initial drying time is in the ascending phase because of surface moisture evaporation and after this phase due to the start of influence of water from within the material to surface descending phase occurs.  Also, the statistical results indicated that thickness at error level of 1% had statistically significant effect on shrinkage and rehydration capacity values of dried potatoes.  Shrinkage percentage increased with increasing of samples thickness. In other words, shrinkage was decreased at different thickness with increasing of infrared radiation power and vacuum level.  It was concluded that the long period of drying and increasing of sample thickness may have contributed to a decrease in rehydration capacity.  Potato slices at thickness of 1 mm put in boiling water for three minutes, the most amount of water absorption ratio that it was able to absorb was the value of 86% the initial moisture.  The results also showed that with increasing shrinkage, rehydration capacity was decreased.