Development of a novel non-water infrared refractance window drying method for Malabar spinach: Optimization of process parameters using drying kinetics, mass transfer, and powder characterization

Abstract

In the present work, a novel non-water Infrared Refractance Window drying (IR-RWD) method was developed for Malabar spinach. Experiments were conducted using a hybrid experimental design. Fresh Malabar spinach was pretreated using the vacuum steam pulsed blanching (VSPB) method. Results showed that VSPB inactivated POD and PPO activities to 9.77% and 5.42% within four cycles, respectively. The optimum conditions were found at 1.2 mm sample thickness, 40% infrared power, and 3.67 cm distance between IR emitter and glass plate resulting in 67.38 % chlorophyll retention, 7.72 overall color changes, 16.57 mgGAE g−1 total phenolic content, and 11.20 kJ kg−1 specific energy consumption. The Page model showed the best fit to the drying kinetics. Furthermore, Biot number indicated the impact of both internal and external resistance on moisture diffusivity. XRD and FESEM characterization of dried powder showed a semi-crystalline phase and square plate, porous morphology. The non-water IR-RWD was a promising alternative to traditional water RWD.