Effect of early harvest on the aroma compounds and bioactive properties of natural olive oils

Abstract

In this study, the effect of harvest time on various quality characteristics of natural oils obtained from Kilis yağlık variety olives was determined. Free fatty acid (FFA), acid number, peroxide value, iodine number, refractive index, color, total phenol (Folin Ciocalteu) and antioxidant capacity (DPPH) values were determined in olive oils. Volatile compounds in olive oils were obtained by solid phase microextraction (SPME) and detected by gas chromatography-mass spectrometry (GC-MS). It was determined that %FFA and peroxide values increased as the harvest time progressed. Similar to the total phenol content determined as 516.61 mg GAE L-1 in early harvest and 77.70 mg GAE L-1 in normal harvest, antioxidant capacities also decreased with ripening. A total of 37 different volatiles were determined in olive oils, and a decrease in aldehyde ratio and an increase in alcohol and acid ratios were detected with ripening. While the rate of pleasant compounds (hexanal, α-farnesene, etc.) was high in early harvest olive oil, an increase in the rate of off-flavor compounds (acetic acid, nonanal, etc.) was observed in normal harvest olive oil. It has been determined that harvest time is an important factor in olive oil quality.