LC-DAD-ESI-MS/MS elucidation of health-promoting phenolic compounds and antioxidant properties of naturally fermented table olives from cv. Gemlik

The main objective of this study was to compare phenolic compounds, antioxidant activity, and other important quality parameters of fresh and naturally fermented green table olives cv. Gemlik. The health-promoting phenolic compounds of fresh and fermented olives were identified by liquid chromatography coupled to diode array detection and electrospray ionisation tandem mass spectrometry (LC-DAD-ESI-MS/MS). A total of 21 phenolic compounds were identified in fresh and fermented table olive samples. The higher level of phenolic compounds was determined in the fresh olives rather than the fermented olives. Oleuropein was the principal phenolic component in the fresh olives while luteolin and hydroxytyrosol were the main phenolic components in the fermented olives. The amounts of luteolin, apigenin, quercetin, and hydroxytyrosol were higher in the fermented olives, when compared to the fresh olives. According to sugar analysis, sucrose, glucose, and fructose were determined in both fresh and fermented olives, and the total amount of these sugars decreased due to fermentation. Glucose was determined to be the dominant sugar in fresh and fermented olives. The results of this study showed that, although the fermentation caused significant decrement of phenolic content, the fermented table olives are still important sources of phenolic compounds and antioxidant capacity.