The effect of antioxidant properties of free and encapsulated rosemary extract in liposome on the oxidation process of canola oil

The antioxidant property of rosemary extract as a natural antioxidant on the oxidation process of canola oil has been reported and compared with the synthetic antioxidant butylated hydroxytoluene (BHT) (at 200 mg L-1). The effect of free and liposomal encapsulated rosemary extract at concentrations of 200, 600 and 1000 mg L-1 was evaluated on improving the oxidative stability of canola oil at 120 degrees C using the Rancimat method. The changes in peroxide value, anisidine, TOTOX and thiobarbituric acid (TBA) have been determined by the Schaal oven test at 60 degrees C. Liposomal rosemary extracts were prepared by the Mozafari method. Then physicochemical properties (Z-potential, particle size and encapsulation efficiency (EE)) were determined. EE and the Z-potential of liposomes were obtained at 54.59% and -65.1 mV, respectively. The particle size of empty and extract containing liposomes was determined 583.5 nm and 265.4 nm, respectively. The total polyphenol content of the rosemary extract by reagent of the Folin-Ciocalteu's phenol was determined as 164.2 mg gallic acid g(-1) extract. Also, the activity of free radical scavenging of both liposomal encapsulated and free extracts, by the 2-2-diphenyl-1-picrylhydrazyl (DPPH) method, were 84.57% and 92.5%, respectively. The induction periods of oil containing liposomal rosemary extract at 600, 1000 mg L-1 and free extract in level 1000 mg L-1 was higher in comparison with samples containing BHT and blank (P <= 0.05). The incorporation of rosemary extract especially in liposome form into oil delayed the oxidation process. Based on the results of this study, to inhibit oil oxidation, rosemary extract, especially in the liposomal form, can be applied instead of synthetic antioxidants such as BHT.