Rosemary extract (RE) is a commercially available natural extract that can be added to food products as antioxidant. This activity is attributed mainly to its phenolic diterpenes carnosic acid and carnosol, and has widely been studied under different conditions, either accelerated storage or at frying temperatures, in the presence or absence of food. Most studies described an antioxidant effect of RE using classical methodologies, such as Peroxide Value or Conjugated Dienes, but these provide limited information on the nature of the compounds being generated. By contrast, 1H NMR spectroscopy has shown to be a great tool to address this kind of study, because it provides information not only about the degradation rate of the oil components, but also about the nature and evolution of the products being formed during the process. Considering all the above, this study aimed to investigate the effect of the addition of RE to sunflower oil oxidation process. RE was added in a proportion that the final concentration of carnosol plus carnosic acid was 0.02 % and the samples were submitted to frying conditions in the absence of food (170 ºC) and to accelerated storage conditions (70 ºC). Aliquots of each sample were periodically analyzed by 1H NMR. It was observed that under frying conditions, RE did not exert a significant protective effect on the oil. Thus, in comparison with non-enriched samples, linoleic acyl group degradation and the formation and evolution of oxidation products were similar. On the contrary, under accelerated storage, RE showed an antioxidant effect, delaying both the degradation of oil components and the formation of primary oxidation products. This led to a delay also in the formation of all secondary oxidation products derived from the former. Therefore, it has been evidenced that the performance of antioxidant compounds can vary under different degradative conditions.
Acknowledgments: PID2021-123521OB-I00/ MCIN,AEI/ 10.13039/ 501100011033/ ERDF,UE and EJ-GV IT1490-22.