Oxidation of Olive Oil under Still Air

Abstract

This work was conducted to analyse the effect of different exposed areas/mass ratios on oil oxidation. Different volumes of the triacylglycerol portion of purified olive oil were placed in glass vials with the same air-exposed area, and stored at 38°C in the dark under still air. The oxidation process was evaluated by determining the peroxide index, K232 and K270 extinction coefficients, fatty acid composition, polar compounds (PCs) and composition of triacylglycerols over time. Substantial differences in the oxidation rate as a function of the air-exposed area to triacylglycerol fraction-mass ratio were observed. The peroxide index exponential increase with time was correlated to the air-exposed area/triacylglycerol fraction mass ratio and the oxidation induction period. Less oxidation derived by-products per gram of triacylglycerols were observed for smaller air-exposed area/triacylglycerol fraction mass ratios. The oxidation process followed an apparent first order chemical reaction. Correlations of the evolution patterns among the various oxidation by-products were also reported.