Abstract: This study evaluated the effects of four drying methods—natural drying (ND), far-infrared drying (FID), heat pump drying (HPD), and microwave drying (MD)—on the physicochemical and structural properties of extruded corn flour. Its microstructure, gelatinization properties, thermal stability, and textural properties were measured and characterized. Scanning electron microscopy (SEM) indicated that compared with that dried by ND, the samples dried by FID (at 60 ℃), MD (at 900 W), and HPD (at 40 ℃) exhibited intact starch granules with smooth and flat surfaces. Furthermore, MD at 2 700 W resulted in the fastest drying rate. Regarding functional properties, FID yielded the most desirable color, while all drying methods significantly reduced the peak, trough, and final viscosities. It was observed that all dried samples formed typical weak gels. The most stable gel, as evidenced by the highest shear force, was identified in the sample dried by FID (at 60 ℃). This sample showed the highest hardness (76.08 g), viscosity (65.06 N), elasticity (0.69), and chewiness (49.39 mJ). Significant differences in physicochemical and structural properties (P < 0.05) were observed among samples subjected to the four drying methods.

Key words: drying; extruded corn flour; physicochemical properties; structural properties