Monitoring the bioactive compounds status of extra-virgin olive oil and storage by-products over the shelf life

The goal of this work was to monitor the phenolic profile of extra-virgin olive oil (EVOO) and of storage by-products in order to achieve a better understanding of the behaviour of these bioactive compounds during storage in the mill companies. Olive oil was stored in 1000-L tanks for 10 months. Qualitative and quantitative variations of the bioactive polyphenols over time were evaluated by high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (TOF-MS) method. Half-life, and elimination, and appearance rate constants (Kel and Ka, respectively) were established for the main phenolic compounds characterized in the samples. When the correlation for the pair oleuropein aglycone or decarboxymethyl oleuropein aglycon and their hydrolyzed derivatives was evaluated, the determination coefficients (r2) were higher than 0.950. On the other hand, at all stages of the storage, by-products exhibited a higher hydroxytyrosol content than did olive oil because its Ka was higher in the by-products than in the olive oil. The results could have a dual application: to determine the freshness:ageing ratio of an extra-virgin olive oil, and to establish the optimal time for collecting the storage by-products as an alternative source of polyphenols with bioactive properties.

► Evolution of the phenolic compounds over time in olive oil and storage by-products.
► Hydrolysis/oxidation of the main phenols in olive oil during storage.
► Mathematical functions to estimate the correlations between the main phenols and specific derivatives.
► Half-life, elimination and appearance rate constants for the main phenolic compounds.
► By-product exhibited in all stage of the storage, higher content in hydroxytyrosol than olive oil.