Effect of rosemary extract on sunflower oil degradation studied by 1H NMR: Differences under frying conditions and accelerated storage

The antioxidant capacity of rosemary extract (RE) has been widely studied using classical methodologies, which offer limited information. Instead, Proton Nuclear Magnetic Resonance (¹H NMR) informs about the degradation rate of oil components and the nature and evolution of the products formed. This study aims to investigate the effect of RE-addition (containing 0.005 % and 0.02 % of carnosol+carnosic acid) to sunflower oil on its degradation under frying conditions without food (170 ± 5 ºC) and accelerated storage (70 °C) by ¹H NMR. In the former, changes in oil viscosity and colour were also studied. During frying, the commercial RE added did not protect the oil, being the degradation of linoleic very similar to control. In contrast, under storage, RE behaved as an antioxidant, mainly at the highest RE-concentration, delaying the degradation of oil components and the formation of oxidation products. Thus, the effect of RE-enrichment on oil degradation depends on the conditions the oil is subjected to.