Advances in drying kinetics and energy optimization of African (Nigerian) walnut ( <i>Tetracarpidium conophorum</i> ): a rapid review

African walnut (Tetracarpidium conophorum) is a highly nutritious oil-rich nut characterized by high moisture content, making it vulnerable to microbiological degradation and lipid oxidation. This review highlights advances in drying technologies, focusing on drying kinetics, energy efficiency, and quality retention of African walnuts and related oil-rich nuts. A structured search of scientific databases (from 2018 to 2026) identified 412 studies, of which 42 met the inclusion criteria. Results show that drying performance depends strongly on the technology applied. Freeze-drying is characterized by good retention of bioactive compounds (80-95%) and reduced oxidative rancidity but is energy intensive (6.5-8.5 kWh/kg of water removed). Infrared and microwave-assisted drying reduce drying time by 40–60% and achieve energy savings of up to 30%. Hybrid systems (such as microwave-hot air, infrared-hot air, and solar-assisted drying) enable energy savings of 20-35%, while antioxidant retention is maintained at 70-85%. The Midilli-Kucuk and Page models best describe the drying kinetic behavior of oil-rich nuts (R² ≈ 0.96-0.999). Artificial intelligence-based modeling enhances drying kinetics modeling and optimization. However, research on African walnut remain limited, and most findings are obtained from other oil-rich nuts. In conclusion, hybrid and energy-efficient drying technologies seem promising for efficient processing of African walnuts.