Enhancing drying efficiency and physicochemical & antioxidant properties of germinated brown rice through microwave incorporation

This study investigates the effects of hot air drying (HAD), microwave drying (MD) and hot air microwave rolling-bed drying (HAMRD) on the drying quality of germinated brown rice (GBR) using freeze-drying (FD) as a control. Our findings revealed that MD and HAMRD further shortened drying time by over 40 % and 71 % compared to HAD, respectively. The effective water diffusion coefficient (D_eff) and water activity (a_w) of HAMRD were in the range of 8.56 × 10⁻¹⁰-1.29 × 10⁻⁹ m²/s and 0.31–0.33, respectively. MD0.8W/g owned the lowest ΔE value (1.87) among all samples. Temperature increase and microwave radiation decreased the relative crystallinity of starch, but enhanced the gelatinization degree. The lowest hardness (106.57 N) and cohesiveness (0.11), highest adhesion (20.71 N) and chewiness (9.73 N) were observed in HAMRD 70 °C. The average content of protein, total phenols, and total flavonoids in HAMRD were 111.32 μg/g, 6.73 mg/g, and 4.11 mg/g, respectively. The average antioxidant capacities of DPPH and ABTS in HAMRD were 16.87 μmol TE/g DW and 11.32 μmol TE/g DW, respectively. Compared with the other three drying methods, HAMRD is a more efficient and promising alternative for drying GBR, balancing quality preservation and drying time.