Long-Term Preservation Evaluation of Extra Virgin Olive Oil by Lipid Hydroperoxides and Malondialdehyde Toxicological Concern Levels

Our study evaluates the long-term preservation of extra virgin olive oil (EVOO) (using the Koroneiki monovariety Olea europaea var. Microcarpa alba, from the Aitoloakarnania region in Western Greece) as a function of storage temperature, duration, and ±gaseous N2 purge under dark conditions by introducing the following innovative tests (applicable to all plant oils): (i) a peroxide value (PV) test that is specific for EVOO′s lipid hydroperoxides (designated PVLOOH), the early-stage peroxidation product of polyunsaturated fatty acids (PUFAs), in contrast to the established nonspecific, unreliable, and less-sensitive iodometric test; and (ii) a test for EVOO′s free malondialdehyde (MDA), the late-stage peroxidation aldehydic product of PUFA, for measuring the Threshold of Toxicological Concern (TTC) for MDA dietary exposure levels (designated TTCMDA-EL), a TTC concept that allows establishment of a level of exposure above which a toxicological concern may occur. It was found that the particular EVOO variety shows the best long-term preservation conditions with minimal change in PVLOOH levels when stored at −20 °C for up to 1.5 years, regardless of ±N2 purge; storage at 5 °C represents the second optimum condition, where PVLOOH levels increase by 40% at +N2 purge up to 1.5 years of storage. It was also found that TTCMDA-EL levels follow a similar trend to PVLOOH across the tested long-term preservation parameters. The study also introduces a minimum TTC dietary exposure level for MDA (TTCMDA-ELmin), which reflects the most optimum extraction procedures and storage conditions for EVOO, relevant for all commercial plant oils and derived food products.