Document Type : Original Article
Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran 2
Golestan Research Center of Agricultural Sciences and Natural Resources, Gorgan, Iran
This study was conducted to find the effects of fruit ripening and extraction method on the quantity and quality of the Koroneiki olive oil. The oil samples extracted in six ripening stages were used for further quality analysis. Quality assessment of the oil was conducted according to the standard methods and the composition of fatty acids was measured by gas chromatography. The results showed that there were some significant differences in the percentage of oil among different fruit tissues and harvesting times. In all tissues, the percentage of oil in dry matter increased significantly from 12 Oct to 4 Jan. The mesocarp and seed had significantly higher percentages of oil compared to endocarp. The extraction method and harvesting time had some significant influences on peroxide value. Furthermore, the extraction method showed a significant effect on the refractive index, but not on the other quality traits studied. The oil extracted using soxhlet had higher peroxide value, but lower refractive index compared to the oil extracted by centrifugation. The harvesting time showed some significant effects on the percentage of free fatty acids, K232 value, K270 value and the amounts of total chlorophylls and total carotenoids. There were a higher percentage of free fatty acids in the oil samples produced in later harvesting times. The oil extracted on 1 Mar showed the highest percentage of free fatty acids. On the other hand, the oil samples obtained from earlier harvesting times had higher values of K232 and K270 and higher amounts of total chlorophylls and carotenoids. The results showed an increase in the percentage of oleic acid and linoleic acid during the harvesting times; while, there was a slight decrease in the percentages of other fatty acids studied.