Title : Effect of Different Storage Conditions on Quality Parameters of “Mild” Extra Virgin Olive Oil
Abstract:
“Mild” extra virgin olive oil (EVOO) is highly appreciated by consumers as it is characterised by lower bitterness and spiciness, parameters which are positively correlated with the concentration of phenolic compounds. Phenols, together with tocopherols, are strong antioxidants present in olive oils, and they contribute to counteract lipid oxidation. The aim of this study was to evaluate whether the low level of phenolic compounds have an impact on the quality/stability of “mild” EVOO stored up to 6 months (t6) under different storage conditions (optimal, 25 °C, 40 °C, 50 °C, 60 °C in the dark and 25 °C at an intensity of 1000 lux, to simulate sales shelf conditions). EVOO samples were collected from different countries, and the number of peroxides, UV absorbances, fatty acids, tocopherols, hydrolysed phenols, and volatile profile, among others, were determined during the storage periods. Under optimal conditions, all the samples at t6 showed values of peroxides, UV absorbances and fatty acids within the legal limits reported in the Regulation (UE) 2019/1604. During storage, no statistically significant differences were highlighted in the content of tyrosol and hydroxytyrosol. By contrast, the concentration of α-, γ-, and δ- tocopherol drastically decreased, indicating their protective role against the oxidation of the lipidic and phenolic fractions. Around 70 volatile compounds were identified, with no significant variations between samples at t0 and t6. The green and floral aromatic notes were expressed by the predominant C6 alcohols and aldehydes (e.g., (E)-2hexenal, 1-hexanol), with (E, E)-2,4-hexadienal being the most impactful in terms of sensorial perception thanks to its low odour threshold, while acetic acid (negative note) resulted high in some samples. The conducted study demonstrates that, although the low level of antioxidant compounds, the quality of “mild” EVOOs is guaranteed over the storage period considered through the study when stored under optimal storage conditions. On the other hand, significant change of the ratio between 1,2- and 1,3-diglycerides with an inversion between them occurred earlier in oil samples stored at higher temperatures while exposure to light caused the decay of tocopherols (55%), which are known to be highly photosensitive.
