Effects of some plant extracts on the oxidative stability of canola oil and its purified triacylglycerols

In this study, the effects of rosemary (Rosmarinus officinalis L.), thyme (Thymus vulgaris L.), sage (Salvia officinalis L.) and bay (Laurus nobilis) extracts on the oxidative stability of canola oil and its purified triacylglycerols (TAGs) were studied. The effects of extraction solvents (methanol, ethanol and acetone) on the extraction yields, phenolic contents and antioxidant activities of these plant extracts were also determined. Methanol extracts had the highest total phenolics (78.4-177.4 mg gallic acid equivalent/g extracts), with the exception of thyme extract. In linoleic acid emulsion, antioxidant activities of all plant extracts were above 89.7% at the studied concentrations. The highest 2,2'-diphenyl-1-picrylhydrazyl radical scavenging activities were found for methanol extracts. There was no significant difference between induction periods of canola oils supplemented with ethanol, methanol or acetone extracts of rosemary, thyme and bay (P > 0.05) in differential scanning calorimeter. Protection factors of rosemary and thyme extracts were higher than those of the sage and bay extracts in canola oil and its purified TAGs in Rancimat test.