Investigation of some quality parameters and oxidative stability of ayvalik olive oils produced by adding olive leaf at different storage conditions

In this study, oil was produced with a two-phase industrial system by adding 2%, 4% and 6% leaves by weight to olive fruits collected in the early and mature harvest periods. The produced oils were stored in a dark environment at room temperature and 12 °C for 12 months. At the beginning of oil production, free fatty acidity, peroxide value, specific absorbance values (K232 and K270) and fatty acid composition were examined. Although free fatty acid, peroxide value, specific absorbance values and fatty acid composition showed partial changes, all oil samples did not exceed the legal limits specified for the Extra Virgin Olive Oil category in the Turkish Food Codex Communiqué on Olive Oil and Pomace Oil (Communiqué No: 2017/26). Oxidative stability (induction periods) increased with leaf addition. While the induction period was determined as 4.05 hours in the early harvest control sample and 4.32 hours in the mature harvest oil sample, it varied between 4.73-4.90 hours in the early harvest oils and 5.18-6.99 hours in the mature harvest oil samples in the leaf supplemented samples. To examine the change in the oxidative stability of oils during storage, peroxide value, specific absorbance values (K232 and K270) were used, and especially the quality parameters of the oil, color (total chlorophyll and total carotenoids), sensory properties and phenolic composition were examined. Peroxide and specific absorbance values showed a fluctuating trend in oils with foliar addition during storage. The samples to which leaves were added before storage were found to be richer than the control sample in terms of color (total chlorophyll and total carotenoids), sensory properties and phenolic composition. During the storage process, leaf addition application in both early harvest and mature harvest oils was found to be richer in terms of color, sensory properties and phenolic substances compared to the control sample. Oils stored at 12 °C showed less decrease in color, sensory and phenolic substances compared to oils stored at room temperature.