Valorization of spent coffee ground as a natural antioxidant and its use for sunflower oil shelf-life extension

In the present paper, spent coffee grounds (SCG) were investigated for their antioxidant capacity, chemical profiling, and their potential to extend the shelf-life of refined sunflower oil (RSO). Ethanolic SCG extract (SCGE) ability to enhance RSO oxidation, during accelerated aging conditions, was examined at 60°C for 120 days. To this end, oxidative stability was evaluated for RSO added with SCGE (at 0.01%, 0.02%, and 0.03%) in the presence of a negative control (RSO without SCGE) and a positive one consisting in vitamin E (VE, a synthetic antioxidant) using the same concentrations (0.01%–0.03%). Our outcomes reveal that SCG were an important source of oil, protein, carbohydrates, minerals, pigments, phenolics, and flavonoid compounds, and they have high antioxidant capacity. SCGE at 0.03% increased RSO oxidative stability by reducing free fatty acids (FFA), peroxide value (PV), and conjugated dienes (CD) and trienes (CT) compared to the unenriched oil. However, both SCGE and VE had no significant effect (p < 0.05) on the fatty acids profile and iodine value. Furthermore, RSO enriched with SCGE had overall acceptability in the sensory evaluation. In conclusion, SCGE improved RSO oxidative stability, and therefore, it could be used as an efficient natural antioxidant to substitute VE during industrial processes.

Practical Application: It is widely accepted that synthetic antioxidants may be harmful to human health. In such a context, plant-based natural antioxidants proved to be an excellent alternative. The valorization of SCG as a natural antioxidant may represent a cost-effective and sustainable approach for the food industry. The addition of used coffee grounds to refined sunflower oil could enhance its shelf-life, offering a potential alternative to synthetic antioxidants. This may also help to reduce the quantity of coffee waste produced, promoting a circular economy.