Evaluation of different variables on the supercritical CO₂ extraction of oat (Avena sativa L.) oil; main fatty acids, polyphenols, and antioxidant content

Six variables (temperature, pressure, static time, dynamic time, chemical pretreatment, and particle size) were evaluated in the supercritical CO₂ extraction of oil from oats (Avena sativa L.), by the responses obtained using a Plackett–Burman statistical design, including the mass of oil extracted, main fatty acids (GC–MS), polyphenols (HPLC), antioxidant activity (ORAC), and total phenolic content (TPC). For the mass of oil extracted, pressure (55 MPa) and particle size (>250 μm) were significant, with a highest yield of 0.800 g/20 g oat. Oleic acid was the most abundant fatty acid (45–53%), followed by linoleic (36–42%) and palmitic (12–16%). Fatty acid composition was significantly affected by particle size, pretreatment, and temperature. The polyphenols vanillin (43.33 μg/g oil), ferulic acid (53.6 μg/g oil), vanillic acid (0.78 μg/g oil), and coumaric acid (2.2 μg/g oil) were detected. Pretreatment and high temperature were significant for increasing the polyphenol content of the oil fractions. TPC was also increased by temperature and pretreatment (97.1 mg gallic acid equivalents/100 g oil) and showed a good correlation with polyphenols (R² = 82%). Additionally, ORAC antioxidant activity (265 mmol Trolox equivalents/g oil) was significantly affected by pretreatment, temperature (80 °C), and particle size (>250 μm).