Fatty acid and phenolic profile of oil and mineral composition of green unripe and purple ripe olives (Olea ferruginea)

Abstract

The present study aimed to explore fluctuations in fatty acids and phenolic profiles of olive oil extracted from fruits of Olea ferruginea Royle harvested at green raw and purple ripe stages from the district Zhob, Balochistan, Pakistan. First, fruit sampling was conducted on 26th June when green olives appeared on trees; second, purple ripe olives were picked on 26th August. Due to very small size and large pit size, oil is extracted without de-pitting the fruit. High-performance liquid chromatography–mass spectrometry (HPLC-MS) system was used for fatty acid and phenolic profiling of both oil samples. Results showed that fatty acid composition of oil extracted from raw green and ripe purple olives falls in the normal range set for purity criteria for olive oils and olive pomace oils by International Olive Council 2019 except for behenic, caprylic, capric and lauric in both oils and oleic acid and linoleic acid of oil extracted from raw green olives which do fall in standard ranges. Fatty acid composition of the olive oil showed that the oil is rich in monounsaturated fatty acids (range 50.71% in oil of green olives and 58.77% in oil of ripe purple olives), polyunsaturated fatty acids (range 30.45% in oil of raw green olives and 19.32% in oil of ripe purple olives) and saturated fatty acids (range 15.27–18.58% in olive oil obtained from raw green and ripe purple olives). SFAs showed least variation with ripening stages. There was high concentration of total phenolics in oil obtained from green raw olives (33.41 mg kg−1) as compared to oil of ripe purple olives (18.49 mg kg−1). The present study revealed that alpha, beta, gamma and delta tocopherols showed a uniform trend along with ripening of olive fruit, i.e. there is a clear decline in total tocopherol content of olive oil obtained from ripe purple olives. Green raw olives showed high values of α-tocopherol (192.47 mg kg−1), β + γ-tocopherols (233.65 mg kg−1) and δ-tocopherol (1087.48 mg kg−1). The present work concludes that ripening of olive fruit affects chemical composition of olive oil.