Investigation of the effect of locality and processing technique on phenolic compounds of Gemlik variety black table olives

In this study, the effects of location and processing methods on chemical composition, phenolic compounds, antioxidant capacity and the other quality parameters were determined and differences have been tried to put forth on Gemlik varieties olives obtained from different regions of the province of Bursa (Mudanya Merkez, Mudanya Çağrışan, Orhangazi, İznik Müşküle and Umurbey) and table olives that processed by dry-salted, pickled and rapid methods during the fermentation period. Based on the results, it was found that both the location and processing methods have distinctive effects on the chemical composition (dry matter, ash, total acid, pH, salt, reducing sugar and oil content) of olive samples during the fermentation period. Hydroxytyrosol was the main phenolic compound determined in both fresh and processed olives. In the early days of fermentation there were increases in hydroxytyrosol, tyrosol and caffeic acid amounts in all processing methods compared to raw olives while the amounts of the all phenolic compounds were decreased at the end of the fermentation. Compared to fresh olives, total of phenolic compounds of olive samples processed by dry salted, pickled and rapid methods exhibited a decrease of approximately 68%, 54% and 60%, respectively. The highest antioxidant capacity and total phenolic content were determined in Iznik Müşküle samples processing by pickled method while the lowest antioxidant capacity and total phenolic content were determined in Umurbey samples processing by dry salted method for the last day of fermentation. In general, after processing of olive samples there were an increase in L* (lightness) and a* (redness/greenness) values while b* (yellowness/blueness) values of olive samples were decreased. Among the all locations, the highest fruit length, fruit width, seed weight, flesh weight, flesh rate of fruit and flesh/pit weight ratio have been identified in olives processed by rapid method while the lowest values were obtained with dry salted samples. For sensory evaluation, Umurbey olives processed with rapid method had the highest total average score while dry salted Mudanya Merkez samples showed the lowest average score.