Physical and chemical behaviour of Nabali Mohassan single-cultivar olive oil during prolonged storage

BACKGROUND: The effect of storage time on the fluorescence emission intensity and physico-chemical properties of olive oil from the Palestinian cultivar Nabali Mohassan was investigated. Olive oil samples stored up to 7 years were obtained from different olive orchards in Palestine, where prolonged storage is still in use. RESULTS: As a result of oxidation, all fluorescent minor compounds (tocopherols, chlorophylls, pheophytins and phenolic compounds) of olive oil significantly decreased as the storage time increased, whereas viscosity increased (P < 0.05). Until 1 year of storage, the physico-chemical properties of olive oil samples were within the limits of both Palestinian and European quality standards, and minor compounds, although affected by a marked decrease compared to freshly produced oil, were still detectable. After 5 years, a 90% decrease of the fluorescence attributed to tocopherols occurred and, after 7 years, phenolics reached a loss of 90%. CONCLUSION: The analysis of fluorescence, together with other physical measures, was demonstrated to be a useful tool for monitoring oil aging. This is the first report on fluorescent minor compounds of oils obtained from Nabali Mohassan olive cultivar. A better knowledge of this single-cultivar oil could enhance the adoption of the best practices by producers, improving the whole production chain. © 2018 Society of Chemical Industry.