Quality characteristics of Koroneiki olive oil from Zakynthos island (Greece) and differentiation depending on the altitude level

The present study aims to analyze the changes in the quality characteristics of Zakynthos olive oil, Koroneiki cv., depending on the altitude of the olive grove, at three different levels, mountainous, lowland, and coastal. Thirty-six olive oil samples, 12 from each level, were studied in terms of conventional quality indices (acidity, peroxide value and absorption coefficients), color attributes, phenolic characteristics (total phenolic content, antioxidant activity and pigment content) and volatile compounds. Results showed that the samples were of excellent quality and revealed significant variations depending on the altitude level. Total phenolic content and chlorophylls (102.25 mg GAE/kg oil and 8.74 mg PE/kg oil, respectively) recorded their highest content in mountainous level, while antioxidant activity and carotenoid content remained constant at all levels. Volatile compound analysis showed that coastal samples were richer (14.284 mg/kg) recording also the highest total amount of C6 compounds. Statistical analysis of data including Multivariate Analysis of Variance and Linear Discriminant Analysis showed that the altitude level of the olive grove plays an important role in the differentiation of single-cultivar olive oil samples. The highest classification rates were achieved for volatiles per se (83.3%) and the combination of volatiles-quality indices-phenolic characteristics (88.9%) indicating a strong effect of pedoclimatic conditions on Koroneiki cv. olive oil samples.