Comparative evaluation of sun, oven, and microwave drying of grated coconut (Cocos nucifera L.): Linking drying kinetics, microstructure, and oil recovery

ABSTRACT Coconut drying strongly influences oil recovery and final oil quality, yet the mechanistic linkage between moisture removal, structural change, and oil recovery in grated coconut remains insufficiently resolved. This study compared sun drying, oven drying (40–70°C), and microwave drying (100–450 W) of grated coconut by integrating drying kinetics, visual and SEM microstructure, FTIR profiles, oil yield, free fatty acid (FFA), and fatty acid composition. Thin-layer drying behavior was evaluated using the Newton, Page, and Henderson–Pabis models. The Page model provided the best overall description of drying across all conditions ( R ² = 0.984–0.995, with the lowest RMSE and χ² values). Higher oven temperatures and microwave power accelerated moisture removal, with 450 W producing the shortest drying time, although pronounced browning occurred at the highest microwave settings. For detailed oil evaluation, oven drying at 70°C and microwave drying at 200 W were selected as the most suitable representative conditions because they combined efficient drying with acceptable product appearance. Microwave drying at 200 W resulted in the highest oil recovery (57.96 ± 0.20 %) and the lowest FFA content (0.02 ± 0.001 %), whereas oven drying produced an oil recovery of 50.69 ± 0.25 % with an FFA content of 0.05 ± 0.002 %. In comparison, sun drying resulted in the lowest oil recovery (36.70 ± 0.78 %). FTIR and SEM showed better preservation of the lipid matrix and cellular structure in microwave-dried samples. Under the present experimental conditions, microwave drying provided the best balance between drying rate, structural preservation, and oil recovery.