Supercritical CO2 Extraction of Waste Citrus Seeds: Chemical Composition, Nutritional and Biological Properties of Edible Fixed Oils

Seeds of Citrus plants (Rutaceae), an important agro‐industrial waste, are a potential source of valuable by‐products. We studied the chemical composition, the antioxidant profile, and the biological/nutritional properties of fixed oils (SFE oils) obtained by supercritical CO2 extraction (at 300 bar and 40 °C) from seeds of mandarin (Citrus reticulata), lemon (Citrus limon), and grapefruit (Citrus paradisi), discarded by a local agro‐alimentary industry. The yields and compositions of SFE oils were compared to oils obtained by n‐hexane extraction of Citrus seeds in a Soxhlet apparatus (SoxE oils). Linoleic (35‐42%), oleic (22‐28%), palmitic (21‐25%), α‐linolenic (4‐10%), and stearic (4‐7%) were the main oil fatty acids, while monolinolein and dilinolein derivatives represented the main triacylglycerols in SFE oils, determined by GC‐FID and HPLC‐DAD/ELSD techniques. Citrus SFE oils showed lower yields than SoxE oils but similar chemical profiles. Principal components analysis applied to fatty acid and triacylglycerol data indicated that the oils from different seeds tightly clustered. Moreover, SFE oils showed radical scavenging activities (ABTS assays), an inhibitory effect on the growth of murine B16F10 melanoma cells and on the mushroom tyrosinase activity. Citrus SFE oils and de‐coated seeds were also evaluated for their attractant effect on the Mediterranean fruit fly Ceratitis capitata by behavioral assays. The results qualify Citrus SFE oils as a potential natural, environment‐friendly, resource for food/pharmaceutical applications. Practical applications: The environment‐friendly supercritical CO2 extraction of waste lemon, mandarin and grapefruit seeds gives edible fixed oils rich in essential fatty acids, suitable for human nutrition and the preparation of nutraceuticals and pharmaceuticals