Effect of Infrared Drying on Drying Kinetics, Color, Total Phenols and Water and Oil Holding Capacities of Orange (Citrus Sinensis) Peel and Leaves

Abstract

The aims of this work were to determine the desorption isotherms of “Maltaise” orange peel and leaves and to investigate the effect of the infrared drying on the drying kinetics and on the physical and functional properties. The moisture desorption curves showed a sigmoïd shape (type II on the BET classification). GAB was found to be the best model for describing the desorption curves. The infrared drying rate increased, with temperature increasing at the same moisture ratio. High drying temperatures preserved initial color parameter values of “Maltaise” orange peels (from 21.893 ± 0.629 to 24.793 ± 0.525, from 37.973 ± 0.941 to 45.44 ± 0.390 and from 45.350 ± 1.077 to 50.439 ± 0.740 for a*, b* and C, respectively) and leaves (from -5.98 ± 1.651 to -5.276 ± 0.342, from 10.73 ± 1.547 to 16.42 ± 0.174 and from 12.283 ± 2.263 to 17.247 ± 0.384 for a*, b* and C, respectively) and maximal phenolic content. Nevertheless, water and oil holding capacities decreased significantly. Low temperatures gave the best functional properties.