Effect of drying method on drying characteristics and quality of microwave pretreated coix seed

Drying is a critical step in the precooking process of instant cereal production. This study compared the effects of hot air drying (HAD) and infrared drying (IRD)—conducted at 40, 50, 60, and 70 °C—on the drying characteristics and quality attributes of microwave-pretreated (MWP) coix seed. The results showed that drying time was significantly reduced as the drying temperature increased. HAD exhibited a high initial drying rate but often caused surface case-hardening due to rapid superficial moisture evaporation, whereas IRD enabled more uniform internal moisture migration and better preserved the loose internal structure. Activation energies were 21.47 kJ/mol for HAD and 28.75 kJ/mol for IRD, and the two-term model best described both drying curves. Quality analysis, scanning electron microscopy (SEM), and magnetic resonance imaging (MRI) jointly confirmed that IRD at 60 °C yielded the most favorable balance of physical properties and cooking characteristics. Collectively, IRD demonstrates superior applicability to HAD for drying MWP coix seed.