Abstract
To date, for the evaluation of olive oil lipid oxidation, certain oxidative parameters, including free fatty acids (FFAs), peroxide value (PV), and the specific extinction coefficient at 270 nm (K270), have been used, and the use of one parameter alone is insufficient to evaluate oil quality. Volatile compounds such as hexanal, which is directly related to oxidative off-flavour, have the potential to be alternative markers for oil oxidation. However, static headspace gas chromatograph analysis is generally not sensitive enough to quantify oil oxidation markers at the levels required. The HERACLES e-nose (Alpha MOS, France) is based on dual fast gas chromatography technology, which is a dynamic headspace analysis that enables the sensitive and rapid determination of volatile compounds in oils. In this study, as a new approach for evaluating photooxidation of olive oil, the e-nose was employed to determine the concentration of hexanal in olive oil, as an oxidative marker during storage under light. Comparative studies revealed that changes in olive oil hexanal content were similar to those of conventional oxidative indicators during storage under light. The FFAs, PV, and K270 showed good correlations with hexanal concentration. In addition, determining the hexanal content by the e-nose analysis also enabled the evaluation of the antioxidant effect of a-tocopherol added to olive oil on oil quality. These results improve our understanding of the shelf-life of olive oil and provide strategies for maintaining the quality of olive oil through determining the concentration of hexanal using e-nose, in addition to conventional oxidative indicators.
