Influence of Time of Harvest on ‘Adana Topagi’, ‘Gemlik’ Olives, Olive Oil Properties and Oxidative Stability

Abstract

Olives and olive oil containing minor components are Mediterranean foods and they are very important in diet. Harvest time plays a key role in the quality and oxidative stability of olive oil. Adana Topagi and Gemlik were harvested at three different times and the oils were obtained on a laboratory scale. The results showed that as the fruit matured, the oil became less stable due to decreasing total polyphenol content, increasing polyunsaturated (mainly linoleic acid), and decreasing chlorophyll content. While pomological properties of olive fruits and oil content increased total phenol, chlorophyll carotenoid content and antioxidant activity was decreased depending on harvest date for Adana Topagi and Gemlik olives (p < 0.05). The best radical scavenging properties were obtained from Gemlik olives and Adana Topagi extracted olive oils. There was a strong interaction between total polyphenol content and DPPH radical scavenging activity for Gemlik and Adana Topagi olives. Chlorophyl and caretenoid content of Gemlik extracted olive oils were higher than Adana Topagi extracted olive oils during ripening (p ≤ 0.05). Gemlik olives were found to be effective antioxidants on DPPH inhibition and oxidative stability of refined olive oils (p < 0.05). It was found that variety and harvest time has significant effect on both some physical, chemical properties and antioxidant activity of olives and their olive oils.