The determination of some physical, chemical and antioxidant properties of Gemlik olives grown in İznik and their olive oils

In this study, pysical, chemical and antioxidant properties of Gemlik Olives grown in İznik and their olive oilswere investigated during ripenning and their antioxidant activity was compored to that of synthetic antioxidants which are BHA and BHT. The results showed that pysical and chemical properties of Gemlik olives and olive oils were strongly changed during ripenning. It was found that the antioxidant effect of Gemlik olives against free radical DPPH were beter than Gemlik olive oils during ripenning. Moreover phenolic extracts of Gemlik olives were found to be as effective as BHT and BHA and/or their activity were at least comparable to BHT and BHA. However, the activity of Gemlik olives against DPPH were not as high as BHT or BHA. Antioxidant activity of phenolic extracts obtained from Gemlik olives and olive oils, BHT and BHA were also tested at a level of 100 and 200 mg/kg in refined olive oil with or without 1 ppm ferric or cupper ions at 60º C. The results showed that antioxidant activity of Gemlik olive and olive oils were significantly decreased in the presence of prooxicant metal ions Fe+3 and Cu+2 depending on ripenning time. BHT and BHA were found to be most effective antioxidants in refined olive oils stored at 60º C compared to Gemlik olive oils extracts at 100 ppm. However, final harvest Gemlik olive oils were found to be slightly antioxidant were compared to the control. Similarly first and final harvest Gemlik olive extracts at 100 ppm were as effective as BHT and BHA and showed slight antioxidant effect when compared to the control. Gemlik olives extracts obtained from at the begining and end of ripeninng were found to be effective as chelaing agents against Cu+2 ions.