Air Frying as a Heat Pre-treatment Method for Improving the Extraction and Yield of Canolol from Canola Seed Oil

Roasting of canola seeds before oil extraction is essential for producing unique flavors and heat-induced formation of novel phenolic compounds. The current study assessed the efficacy of roasting by air frying as a pre-treatment technique to improve the extraction of canolol and other oil-soluble sinapic acidic derivatives (SADs) from canola seeds. Air frying of canola seeds was performed at temperature and time regimens of 160, 170, 180, or 190 degrees C for 5, 10, 15, or 20 min, respectively. Soxhlet method was used for oil extraction and the soluble SADs were extracted from the oil by addition of an equal volume of hexane/70% methanol mixture followed by quantification using high-performance liquid chromatography-diode array detection (HPLC-DAD). The total phenolic content (TPC) and antioxidative property of the oils were also evaluated. The results indicated a time-temperature association for canolol formation. The optimum air frying condition at 190 degrees C for 15 min generated the highest canolol concentration (1439 +/- 45.6 mu g/100 g roasted seed) in addition to other unidentified SADs. The oil extracts obtained from canola seed roasted at 180, 15 min, 190 degrees C, 15 and 20 min showed the highest TPC (0.387 +/- 0.015, 0.413 +/- 0.002 and 0.419 +/- 0.002 mg GAE/g oil), respectively, and the strongest antioxidant activities (DPPH radical scavenging and iron reducing), but exhibited weak metal ion chelating activity. There was a strong positive correlation of canolol content to the antioxidant activities (DPPH, FRAP) and TPC value for the canola oil extracts (r = 0.85, r = 0.93 and 0.88), respectively.