In this study, Tarom Mahali rice bran extracts by ultrasound assisted and traditional solvent (ethanol and ethanol: water (50:50)) extraction method were compared. The total phenolic and tocopherol content and antioxidant activity of the extracts was determined and compared with TBHQ by DPPH assay and β-carotene bleaching method. The results show that the extract from ethanol: water (50:50) ultrasonic treatment with high amount of phenols (919.66 mg gallic acid/g extract, tocopherols (438.4 μg α-tocopherol/ mL extract) indicated the highest antioxidant activity (80.36 % radical scavenging and 62.69 % β-carotene-linoleic bleaching) and thermal stability (4.95 h) at 120 °C in canola oil. Being high in antioxidant and antiradical potential and high content of phenolic and tocopherol compounds of ethanol: water (50:50) ultrasonic extract caused to evaluate its thermal stability at 180 °C in canola oil during frying process. So, different concentrations of Tarom Mahali rice bran extract (100, 800, and 1200 ppm) were added to canola oil. TBHQ at 100 ppm served as standard besides the control. Free fatty acids (FFAs), Peroxide value (PV), carbonyl value (CV), total polar compounds (TPC) and oxidative stability index (OSI) were taken as parameters for evaluation of effectiveness of Tarom Mahali rice bran extract in stabilization of canola oil. Results from different parameters were in agreement with each other, suggesting that 800 ppm of the extract could act better than 100 ppm TBHQ in inhibition of lipid oxidation in canola oil during frying process and can be used as predominant alternative of synthetic antioxidants.

The susceptibility of essential oil (EO) as an antioxidant for canola oil was studied. Major compounds of the EO were 11-acetoxyeudesman-4-α-ol (26.3%) and α-bisabolol (24.6%). Different concentrations (200, 600 and 1200 ppm) of EO and synthetic antioxidant BHA (200 ppm) were added to canola oil and incubated for 60 days at room temperature. Acid value (AV), peroxide value (PV), carbonyl value (CV), iodine value (IV), total phenolics (TP), total polar compounds (TPC) and oxidative stability index (OSI) of canola oil were determined. Antioxidant capacity of the EO was measured by DPPH and β-carotene-linoleic acid assays. Results exhibited that DPPH and β-carotene-linoleic acid experiment detections on the EO were analogous in high concentrations to those detected on BHA. Moreover, incorporated EO samples had better AV, PV, CV, IV, TP and TPC than control. EO at concentration of 600 ppm indicated higher antioxidant activity in canola oil compared with BHA.

The performance of the sunflower oil in deep-fat frying was assessed by evaluating the efficacy of linoleic acid level and composition of tocopherol isomeric on its frying stability. The oil was used as a frying media to fry potato strips for 6 h daily for 7 days. Standard procedures for the measurement of used frying oil degradation such as fatty acid composition, acid value, anisidine value, conjugated diene value, total polar compounds and tocopherol concentration were used. At analogous composition of tocopherol isomers, the high oleic sunflower oil with smaller value of linoleic acid content indicated higher frying stability than the oil with higher linoleic acid level. This, indicating that the high oleic sunflower oil frying efficiency was depended mainly with the oil linoleic acid content and the composition of tocopherol isomers showed no significant effect. Also, the α-tocopherol degradation was lower compared to the corresponding degradation of γ-tocopherol.

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This study aimed to evaluate the impact of var-