From Waste to Value: Coffee Peel Extracts as Natural Biosynthesis for Metal Nanoparticles and Antioxidant Protection of Edible Oils

This study investigated that coffee peels (Coffea arabica by-products) and their application in the green synthesis of metal nanoparticles for edible oil stabilization. Nanoparticle-enriched treatments demonstrated stronger effects. MgNPs and MnNPs at 800 ppm increased IT to8.56–8.98 h in corn oil and 6.45–6.53 h in sunflower oil, while at 1000 ppm they further enhanced stability (corn: 8.64–8.99 h;sunflower: 6.86–6.99 h).High-performance liquid chromatography (HPLC) revealed that coffee peels are rich in bioactive compounds, particularly chlorogenic acid (3220.5 mg/100 g), along with significant levels of caffeic acid, salicylic acid, epigallocatechin gallate, and kaempferol-3-O-glucoside, confirming their strong antioxidant potential. Transmission Electron Microscopy (TEM) confirmed the formation of spherical nanoparticles with average sizes of 19.7 ± 6.8 nm (Co), 23.9 ± 7.9 nm (Mn), and 28.7 ± 9.3 nm (Mg), highlighting the effective capping and stabilizing role of coffee-derived phytochemicals. The antioxidant performance of Coffee Peel Extract (CPE) and its nanoparticle formulations was evaluated in corn and sunflower oils at 800 and 1000 ppm. Rancimat stability and physicochemical analyses showed that Coffee Peel Extract significantly improved oxidative stability compared with controls. Notably, Coffee Peel Extract with nano magnesium ( CPE-MgNPs) at 800 ppm preserved higher unsaturation levels and maintained moderate peroxide values, while crude CPE at 1000 ppm offered balanced protection. CPE and its nanoparticles demonstrated an effective natural antioxidant activity. These findings highlight on coffee peels as a sustainable and low-cost resource for green nanotechnology and natural antioxidants, offering dual benefits of agricultural waste valorization and edible oils preservation.