Comparation of roasting and vacuum microwave drying treatments on physicochemical properties of supercritical CO2-extracted oil from black sesame seeds

Roasting and vacuum microwave drying are essential pre-treatments for supercritical CO2 extraction of black sesame seeds, enhancing extractability, reducing moisture, and maintaining oil quality. This study compared these pre-treatments with untreated seeds. Roasting at 80 °C and supercritical CO2 extracting at 45 °C and 225 bar achieved the highest oil yield at 47.31 %. Pre-treatments such as roasting and vacuum microwave drying reduced parameters including acid value (8.43–29.39 mg KOH/g oil for roasting and 10.80–34.62 mg KOH/g oil for vacuum microwave drying), free fatty acid percentage (4.24–14.78 % and 5.43–17.40 %, respectively), and peroxide value (1.38–2.59 meq O2/kg oil and 1.10–1.79 meq O2/kg oil, respectively). Roasting at 80 °C and extracting at 65 °C and 175 bar produced oil with the highest sesamin (26.87 mg/g) and sesamolin (16.84 mg/g) content, high phenolic compounds (94.90 μg gallic acid equivalent/g), and flavonoids (0.77 mg quercetin equivalent/g), resulting in strong antioxidant activity with DPPH and ABTS values of 1.29 mg Trolox/g oil each. Oils from untreated seeds had higher phenolic compounds (108.02 μg gallic acid equivalent/g) and flavonoids (4.13 mg quercetin equivalent/g) with slightly lower antioxidant activities, with DPPH at 1.20 and ABTS at 1.28 mg Trolox/g oil. All supercritical CO2-extracted oils had similar fatty acid profiles, including linoleic (36.86–50.95 %), oleic (32.18–42.93 %), palmitic (7.83–9.58 %), and stearic (3.87–5.46 %) acids. Despite decreasing stability over time, oil from roasted seeds showed better stability than commercially cold pressed black sesame seed oil.