Oxidation of mixtures of triolein and trilinolein at elevated temperatures

The aim of this study was to investigate how triolein and trilinolein are oxidised at elevated temperatures (60-220°C) in mixtures with octadecane, used as a saturated diluent. The percentages of triolein/trilinolein and octadecane and the oxidation conditions (temperature and time) were chosen according to a statistical central composite design. Heating was performed in a Rancimat equipment. The extent of oxidation was assessed by measuring the peroxide value by titration against potassium iodide, total polar compounds by solid-phase extraction, triacylglycerol polymers by high-performance size-exclusion chromatography, and the losses of triolein and trilinolein by gas-liquid chromatography. The results indicated that maximum peroxide values were obtained at intermediate temperatures while the formation of polar compounds and polymers were only significant at temperatures above 140°C. Interestingly, under the conditions used, concentration of octadecane was not significant in spite of the wide temperature range selected. Finally, independently of the concentration of triolein and trilinolein in the sample, at temperatures below 140°C only losses of trilinolein were observed.