Effect of the picking time, cultivation site, and cultivar of olive oil characteristics | ||
| Kirkuk University Journal For Agricultural Sciences | ||
| Article 8, Volume 10, Issue 4, December 2019, Pages 68-78 PDF (948.26 K) | ||
| Document Type: Research Paper | ||
| DOI: 10.58928/ku19.10408 | ||
| Authors | ||
| Thamer A. Khalel* 1; Yusef H. Hamo2; Hala M. Najeeb1 | ||
| 1college of Agriculture and forestry / Mosul university | ||
| 2college of Agriculture / Duhok university | ||
| Abstract | ||
| This study has been carried out in using three cultivars of olive (Al-Ashracy, Al-Khistawi, and Arbequina) which are the most cultivars planted in Dohuk province/Iraq. The olive fruits were picked out from olive farms located in Simeel district, named Zawa Farm and Qasara Farm. The time of picking olive fruits was implemented in 15 days intervals during the period between October-December of the season of 2016. The objective of this study was to know the effect of the picking time, cultivar, and cultivation site on the chemical and physical properties, in addition to the storage capacity of olive oil. The olive oil was extracted by two methods (cold method and hot method by using Soxhlet instrunent). The study included the determination of the ratio of oil components of fatty acids and the total polyphenols, in addition to testing the storage capacity of olive oil samples at different temperatures (5, 20, and 30 ⁰C) with its effect on acidity and peroxide value. The cultivation site has a significant effect (P<0.05) on the oil ratio extracted by Soxhlet and the olive trees planted in Qasara site was significantly higher than Zawa site where the percentage of oil extracted were 31.39% and 26.74% respectively and there were significant differences (P<0.05) between different cultivars undertaken in this study. The oil which was extracted by cold method from olive trees cultivated in Qasara site, was significantly higher (P<0.05) than trees cultivated in Zawa site reaching 13.31% and 11.04% respectively. Arbequina cultivar was significantly higher (P<0.05) than both Al-Ashracy and Al-Khistawi towards oil ratio while the oil extracted by cold method gave a significant effect among picking intervals and the selected cultivars. It was observed that a rise in acidity ratio determined as Oleic acid in the oil stored at 30 ⁰C, in comparison with storing at 20 and 5 ⁰C. The last picking time gave the highest acidity where the higher the temperature of storage increased with acidity in oil. The first picking time had recorded the lowest in peroxide value but it was increased during the last picking time. It was found that the acidity of olive oil cultivated in Qasara was high compared with olive fruits of trees cultivated in Zawa site as 2.86 and 2.61 respectively. The acidity values of Al-Ashracy cultivar was significantly higher (P<0.05) than Al-Khestawi cultivar and the later was significantly higher than Arbequina cultivar as 3.24, 3.16, and 1.79 respectively. The amount of total polyphenols declined in oil with the olive picking period delayed from first to fifth picking dates for the all selected cultivars in this study during the harvesting season. The Al-Ashracy trees cultivated in Qasara site gave highest polyphenol amount (272 mg/kg). Polyphenol rate of Arbequina in Zawa site were higher than both Al-Ashracy and Al-Khestawi cultivars as 314, 312, and 297 mg/kg respectively, in comparison with other cultivars of the same cultivation site. Fatty acids ratio differed in oil significantly showing that the fatty acids (oleic, palmitic, linoleic, and linolenic) increased with increasing maturity date. The data were analyzed using SAS program and the means were compared using Dinkin Multiple Interaction at error probability of 5%. | ||
| Keywords | ||
| olive oil; fatty acids; polyphenols; picking time; cultivation site | ||
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