The effect of different harvest periods on the chemical properties and bioactive components of olive oil obtained from Ayvalık, Memecik and Gemlik olives

Determination of the optimum harvesting times of olive fruits is one of the topics that have been studied recently in terms of determining the quality and oxidation stability of olive oils. As the physicochemical properties of olive oil, phenolic compound content, fatty acid composition, tocopherol contents are changed by ripening, it can be used as a criterion in determining optimum maturation period. In order to obtain high quality and high oil yield, it is necessary to collect the olives at the ideal harvesting time. The ideal harvesting time is usually determined by the calculation of the maturation index. Ripening of olives is a slow and gradual process that takes months. The metabolic events of the structure are continuing until the fruit maturity is obtained. For this reason olives harvested early or late have different quality characteristics such as oxidative stability, sensory properties and chemical composition. As a result of the previous studies, the optimum maturation index was determined as 3 and above. In this study; some physicochemical properties such as fatty acid compositions, triglyceride, sterol, tocopherol and phenolic compounds of the oils obtained from Ayvalık, Memecik, Gemlik variety olive fruits consumed widely in our country were investigated. Ayvalık, Memecik and Gemlik olive varieties which constitute the main material of the study were harvested manually in 3 different harvest period (October, November, December) in year 2017. Olive samples; maturation index, moisture content, fat content, fats obtained from fruits; total phenol analysis, UV specific absorbance analysis, total chlorophyll and carotenoid analysis, fatty acid composition, triglyceride composition, sterol composition, α-tocopherol and phenolic compound analysis were performed. The results obtained were compared to previous studies and the values presented in Turkish Food Codex, Edible Olive Oil and Pirina Oil Dispensation (2017/26). The results were evaluated by SAS statistical analysis package program.