The effect of fatty acid profile on the stability of non-traditional and traditional plant oils

Abstract

The effect of fatty acid composition on the autoxidation of selected plant oils (rapeseed (canola) oil, corn oil, frying oil, grapeseed oil, pomace olive oil, rice bran oil, sunflower oil and high oleic sunflower oil) during their storage was studied. Oils were purchased in retail food stores. Oxidative stability of plant oils was monitored during the storage under the Schaal test conditions at 60 °C in 100 mL beakers and the dark for 40 days. The weight changes, the peroxide and acid values were analysed during the storage. Changes in the composition of fatty acids were analyzed by the gas chromatography-mass spectrometry. The results obtained by monitoring the weight changes of oils correlated with their peroxide values. The induction period in case of grapeseed and sunflower oils was 27 and 28 days respectively. The induction period for frying and rapeseed oils were around 35 days. The remaining four oils had induction periods over 40 days. The acid values at the end of experiment correspond to both the relative weight gain and the the peroxide values. The stability of oils depended mainly on the degree of fatty acids unsaturation. A strong negative correlation between oleic acid content and oil stability expressed as the peroxide value was found. The significant positive correlation was found in case of linoleic acid. The relative content of polyunsaturated fatty acids decreased during the storage while the content of saturated and monounsaturated fatty acids increased. The highest relative increase in oleic acid was found at the least stable oils, grapeseed and sunflower oils, by 37.5% and 25.3% respectively. The initial content of free fatty acids monitored by the acid value did not affect the oxidation rate. With consideration to all monitored parameters the grapeseed and the sunflower oils were the least stable. The most stable ones were olive pomace and high oleic sunflower oils.