An efficient and clean extraction approach for hazelnut oil with high ceramide: Enhanced biological properties and abundant flavor complexity

This study optimized the extraction of hazelnut oil (HO) using subcritical water extraction (SWE), achieving a maximum yield of 42.80% under conditions of 210 °C, 30 min, and a solid-to-liquid ratio of 1:10 g/mL. SWE-derived HO (SW-HO) was compared with commercial (P-HO), cold-pressed (CP-HO), and Soxhlet-extracted (S-HO) oils. All HO types contained over 92% unsaturated fatty acids (UFAs), with SW-HO showing the highest contents of palmitoleic and oleic acids. SW-HO exhibited distinct caramelized flavor, which was attributed to abundant furans and pyrazines. Lipidomics revealed significantly higher ceramide (Cer) content in SW-HO, which demonstrated superior antioxidant activity and significantly enhanced RAW264.7 macrophage proliferation at 400 μg/mL. These findings suggest that SWE effectively produces high-quality HO with elevated bioactive components (Cer, total phenol, and UFAs), enhancing functional properties and sensory attributes. This work provides both technical and theoretical support for the functional preparation and development of HO. • SWE enables simultaneous heat pretreatment and extraction for hazelnut oil. • SW-HO had the highest content of unsaturated fatty acids (palmitoleic and oleic acids). • SW-HO, richest in aldehydes, ketones, furans, pyrazines, and pyrroles, endows desired flavor. • Lipidomics showed the highest ceramide content in SW-HO compared to other groups. • The high ceramide content of SW-HO promotes its functional properties.