Impact of Oven and Microwave Drying on the Kinetics and Microstructure of Avocado (Persea americana) Pulp

Avocado (Persea americana) contains a high lipid content in its flesh, making it a promising source of value-added vegetable oil. However, the high initial moisture content in the avocado mesocarp presents a significant challenge in the drying and oil extraction processes. This study investigates the effects of two drying methods—oven drying and microwave-assisted drying—on moisture removal kinetics, microstructural changes, and oil yield from avocado. Drying kinetics were analyzed using four semi-theoretical thin-layer models: Newton, Henderson–Pabis, Logarithmic, and Midilli et al. The results indicated that the Midilli et al. model provided the best fit for both drying methods, with a coefficient of determination (R²) greater than 0.99 and the lowest RMSE values. The effective moisture diffusivity (Deff) ranged from 6.93 × 10⁻¹⁰ to 4.83 × 10⁻⁸ m²/s, with higher values observed in microwave drying, indicating faster moisture transport compared to oven drying. Microstructural analysis using scanning electron microscopy revealed that oven drying produced a porous structure with relatively intact cell walls, while microwave drying caused tissue collapse due to localized overheating. These microstructural differences directly impacted oil yield, with oven-dried samples yielding more oil (38.65%) compared to microwave-dried samples (37.18%). Overall, low-temperature oven drying was found to be a more effective pretreatment for avocado oil extraction, as it preserved cell structure integrity while enhancing oil yield. This research provides critical insights into optimizing avocado oil production, emphasizing the importance of effective pre-drying methods that maximize yield while maintaining the quality of bioactive compounds.