The Effect of Harvest Period on Total Phenolic Content, Phenolic Compounds and Peroxide Value in Oil of Four Olive Cultivars Grown in Şanlıurfa

Cultivar and harvest season relationships affect olive oil quality characteristics. This research aims to investigate the effect of four different olive cultivars, ‘Arbequina’, ‘Ayvalık’, ‘Gemlik’ and ‘Nizip Yağlık’, grown under Şanlıurfa conditions on the total phenolic content, phenolic compounds and peroxide value of olive oils in three different harvest periods (October, November and December) in both 2020 and 2021. The results showed that all parameters significantly changed during harvest periods, and in general, the best results were obtained from olives harvested in October. Among cultivars, the olive oils of ‘Gemlik’ (474–496 mg gallic acid equivalent/kg) and ‘Nizip yağlık’ (297–514 mg gallic acid equivalent/kg) cultivars had the highest total phenolic content. The cultivar ‘Gemlik’ had the highest average peroxide values in both years as 3.61 and 3.16 meq O2/kg. Although there were differences between the cultivars in terms of peroxide values, all of these values were below the legal limit of 5 meq O2/kg (refined olive oil), which is the highest quality value. The ‘Ayvalık’ cultivar, in particular, draws attention with its high hydroxytyrosol content, offering consumers a healthier alternative. The ‘Nizip Yağlık’ cultivar was determined to have the highest p-coumaric acid value. The ‘Gemlik’ cultivar and the harvest conditions in October bring together ideal conditions for the amount of resveratrol.