Effect of Extraction Method on the Physicochemical Properties, Bioactive Compounds, and Oxidative Stability of Oils from Rosehip, Japanese Quince, Grape, and Strawberry Seeds

Fruit seeds generated during fruit processing are promising sources of valuable oils and bioactive compounds, but extraction conditions can strongly affect the quality of the recovered lipid fraction. This study compared Soxhlet extraction, room-temperature hexane extraction, and the Folch method for extracting oils from rosehip, Japanese quince, grape, and strawberry seeds. The extracted oils were evaluated for extraction yield, physicochemical quality, fatty acid composition, nutritional lipid indices, pigment content, total phenolic content, antioxidant activity, and oxidative stability measured by pressure differential scanning calorimetry. Oil extraction yield ranged from 4.34% to 10.76% and depended mainly on seed type. All oils were rich in unsaturated fatty acids, with polyunsaturated fatty acids (PUFAs) predominating in rosehip, strawberry, and grape seed oils, whereas Japanese quince seed oils showed the highest monounsaturated fatty acid (MUFA) fraction. The Folch method generally enhanced recovery of carotenoids, chlorophyll-related pigments, phenolic compounds, and antioxidant activity, but it also resulted in higher acid value (AV), peroxide value (PV), para-anisidine value (p-AnV), Total Oxidation Value (TOTOX), and Integral Oxidation Value (INTOX). Japanese quince seed oils, especially those obtained by Soxhlet and room-temperature hexane extraction, showed the highest oxidative stability, whereas Folch-extracted grape and strawberry seed oils were the least stable. Overall, extraction method affected oil quality and bioactive compound recovery more strongly than fatty acid composition.