Proximate Composition, Antioxidant Activity, Lipids and Elemental Profiling of Argan, Almond, Sesame, Nigella, Soybean and Sunflower Oil Press Cakes Reveal a Great Potential of Valorization

Abstract Purpose : The oil industry generates substantial quantities of oilcake. These residues are traditionally used in many domains for multiple purposes. In order to explore other potential uses of these by-products, a comprehensive physicochemical characterisation was conducted. Methods : The analysis encompassed various parameters, including mineral profiling, protein content, fiber content, fatty acid composition, sterol content, total polyphenol, total flavonoid content, and antioxidant activity in argan, almond, sesame, nigella, sunflower, and soybean press cake. Results : Results indicated that potassium (K), phosphorus (P), magnesium (Mg), calcium (Ca), and sodium (Na) constituted the primary mineral elements in the studied oilcake. Regarding protein content, argan and soybean press cakes contained the highest level of 45.90±0.10 and 44.85±1.10 g/100g, respectively, while nigella and sunflower press cakes had the lowest protein content of 25.62±1.99 and 26.43±2.06 g/100g, respectively. The fatty acid composition revealed that the residual oils extracted could present beneficial properties, as they are rich in unsaturated fatty acids. Nigella press cake oil has a high oleic acid content (67.65%), while Sunflower press cake oil is richest in linoleic acid (54.17%). Sunflower press cake outperformed in total phenolic and flavonoid content, with registered values of 9.82 mg GAE/g and 15.44 mg QE/g, respectively. Additionally, sunflower press cake demonstrated the highest DPPH and FRAP antioxidant activity, and the values were 34.05 and 8.90 mg AAE/g, respectively. Conclusion : The findings suggest that oilcake could be considered as a rich nutrient source and their extracts exhibit substantial potential for added value, warranting focused attention in future research and development.