Effect of microwave-assisted magnesium oxide blanching and hybrid drying on color retention in dried okra

This study aimed to investigate the effects of microwave-assisted magnesium oxide (MgO) blanching combined with hybrid drying on color retention, drying kinetics, and quality attributes of dried okra. Fresh okra (cv. Lady’s Finger) was subjected to five pre-treatment conditions: (1) untreated (F-Okra), (2) hot-water blanching at 90°C for 3 min (B-Okra), (3) hot-water blanching in 0.1% MgO solution at 90°C for 3 min (B+MgO-Okra), (4) microwave blanching at 720W for 2 min (MW-B-Okra), and (5) microwave-assisted blanching with 0.1% MgO at 900W for 5 min (MW-B+MgO-Okra). Samples were subsequently dried using three methods: tray drying (TD: 60–80°C), microwave drying (MW: 450-900W), and hybrid microwave-tray drying (MW 900W for 5 min followed by TD at 60–80°C). Drying kinetics were evaluated using eight mathematical models, with the Logarithmic and Midilli-Kucuk models providing the best fit (R2 = 0.999). Moisture content water activity, and color parameters (L*, a*, b*, and a*/b* ratio) were measured. Results indicated that pre-treatment method and drying conditions significantly influenced (p < .05) drying time, final moisture content, and color preservation. The combined microwave-assisted MgO blanching followed by hybrid drying at 70°C reduced total drying time from 570 to 210 min while maintaining the highest greenness index (a*/b* = -1.62) and achieving low water activity (aw = 0.44), suitable for microbial stability. Sensory evaluation revealed acceptable quality compared to commercial products. This integrated approach demonstrates a feasible, energy-efficient, and oil-free strategy for developing crispy, visually appealing okra snacks with improved processing efficiency and enhanced chlorophyll retention.