Effect of methanolic garlic, rosemary and olive leaves extracts on some chemical properties of canola oil

Rapeseed oil is prone to oxidation because of high unsaturated fatty acids. Using synthetic antioxidant due to the possibility of toxic and carcinogenic effects is limited. Thus, it is important to seek on replacing synthetic antioxidants by natural antioxidant. Antioxidant treatments used in this study were included 10 different mixture containing garlic, rosemary, olive leaf, and a sample without antioxidants as a control and a sample containing TBHQ as a synthetic antioxidant. The induction period in Ransymat at 110°C was determined. Tocopherol content, fatty acid composition and polyphenols was investigated before and after heating at 180 ° C. Results showed that B4 (0% garlic +10% rosemary + 0% olive leaf) has the highest tocopherol content. The results of rancimat showed that A2 (5% garlic +5% rosemary + 0% olive leaf) with 113.2 ppm polyphenol, was the most stable sample (25.7h) compared with control samples (9.2 h) and samples containing TBHQ (15 h). Considering possible negative effects of consumption of synthetic antioxidants on health and also results of this study, it can be suggested A2 (5% garlic + 5% Rosemary + 0% olive leaf) as a substitute of TBHQ to maintain quality of rapeseed oil.