Chemical Composition of Monovarietal Extra Virgin Olive Oils Obtained from Tunisian Mills: Influence of Geographical Origin

Comprehending the variability in the chemical composition of olive oil from the same olive variety, based on its geographical origin, is essential. This study investigated the chemical composition of Chétoui olive oils from thirteen mills located in Northern Tunisia's Béja region. The chemical composition of olive oil exhibits substantial regional variability. Free acidity ranged from 0.57% to 0.73%, and peroxide values varied between 7.33 and 14.00 meq O2/kg. Total phenolic content varied as well, with values ranging from 906.53 to 1,298.60 caffeic acid eq/kg (oils from Amdoun and Testour II, respectively). Chlorophyll contents ranged from 2.03 to 7.85 mg/kg, and carotenoids from 1.28 to 3.92 mg/kg. Olive oils from Amdoun and Dogga II were the richest in these compounds. In terms of tocopherols, the range extended from 282.88 mg/kg (oil from Tibar) to 416.79 mg/kg (oil from Testour II). DPPH radical scavenging activity of the polar fraction of all olive oils was higher than that of the non-polar fraction. Fatty acid profiles were mostly similar with exception of the oil from Tibar with lower saturated fatty acid content and higher monounsaturated fatty acid content. Substantial differences in polyunsaturated fatty acid content were found. Triacylglycerol compositions differed as well, with the lowest triolein percentage around 13.66% and the highest at approximately 34.98%. In summary, this study reveals significant regional variations in the chemical composition of Chétoui monovarietal olive oil, highlighting the collection region impact on oil quality and nutritional properties.