Optimizing drying techniques for turmeric (Curcuma longa L.): impacts on color, curcumin, and essential oil composition.

Turmeric (Curcuma longa L.) is primarily traded in dried form; preserving its bioactive compounds and quality through optimal drying methods is critical. This study evaluated the effects of various drying techniques-sun drying (SD), convection oven drying (COD), vacuum oven drying (VOD), infrared drying (IRD), microwave drying (MD), and freeze drying (FD)-on turmeric rhizomes slices. Key parameters analyzed included moisture loss, color, total phenolic content (TPC), curcumin content, antioxidant capacity and essential oil (EO) content and composition. FD demonstrated superior performance, achieving the brightest yellow color, the lowest browning index (17.07), the highest antioxidant capacity, TPC (78.90 mg GAE/g), curcumin content (3.83 %), and EO yield (4 %), with ar-turmerone and α-zingiberene as dominant components. While FD excelled in quality preservation, MD and IRD emerged as efficient alternatives due to their faster processing times and lower energy consumption, offering energy-efficient solutions for high-quality turmeric drying.