Valorization of turmeric (Curcuma longa L.) rhizome: Effect of different drying methods on antioxidant capacity and physical properties

Turmeric has high commercial demand internationally, owing to its high nutrient and medical value. In this research, turmeric samples were subjected to several drying methods viz. infrared freeze drying (IRFD), freeze drying (FD), and pulse-spouted microwave-assisted freeze-drying (PSMFD). Over the range of operating conditions employed in this study, IRFD of infrared radiation was showed to shorten the drying time by 21.27% relative to FD, while the retention valves of ascorbic acid, curcumin, total phenols, and total flavonoids remains at 75.61%, 94.06%, 69.00%, and 80.09%, respectively over the range of experimental parameters. IRFD significantly (P < 0.05) reduced 25.19% of the energy consumption in comparison with FD. Furthermore, the interior of IRFD samples exhibited a honeycomb porous structure, and increased hardness, lower shrinkage, apparent density compared to PSMFD. Additionally, IRFD also performed better than PSMFD and FD under vacuum freezing conditions.