FRUIT AND OIL CHARACTERISTICS OF THE MAIN SYRIAN OLIVE CULTIVARS

Headnote

ABSTRACT

In the three-year period 2004-06, a study was carried out to characterise the fruit and oil of the main Syrian olive cultivars: Kaissy and Zaity in the Aleppo area, Dan, Hemplasi and Souri in the Damascus area, Insassy, Karamani and Sorani in the Idleb area, Khodeiri in the Lattakia area, Safrawi in the Hama (Mousiaf) area and Doebli in the Tartous area. Olive samples were collected in October or November and the fruit weight, epicarp and mesocarp pigmentation and oil content were determined. Oil was also extracted from the samples and the acidity, peroxide value, spectrophotometric absorbance at 232 and 270 nm (K^sub 232^ and K^sub 270^) and ΔK, fatty acid composition, sterol composition and content and erythrodiol + uvaol content were determined. Marked differences were recorded in the cultivars for all the fruit characteristics studied. The oleic acid content was around 70% in most of the oils. The Karamani cultivar had a low oleic acid value (60%) and high palmitic and linoleic acid values. The average values of the parameters (acidity, peroxide value, absorbance in ultraviolet, fatty acid composition, sterol composition and content, erythrodiol + uvaol content) used to evaluate oil quality were within the International Olive Council (IOC) trade standards for extra virgin olive oils, with the exception of Δ-7-stigmastenol values which were higher than 0.5%, the maximum value established by such standards, in the cultivars Khodeiri and Doebli. The average Δ-7-stigmastenol values were as high as 0.5% or very close to 0.5% in the cultivars Insassy and Sorani, respectively, indicating that, also in some replicates of these cultivars, the Δ-7-stigmastenol values were higher than 0.5%.

- Key words: apparent β-sitosterol, erythrodiol + uvaol content, fatty acid composition, olive germplasm, Olea europaea L., Δ-7-stigmastenol, sterol compostion and content, Syrian olive oil characteristics -

INTRODUCTION

Syria, being part of the original habitat of Olea europaea L., has a very rich olive germplasm. Although there are about seventy varieties cultivated in the different areas of the country (NSEIR et al, 1985; GCSAR, 2007), there are very few that have been extensively cultivated. In fact, five cultivars, Zaity, Sorani, Doebli, Khodeiri and Kaissy, represent about 90% of the total olive trees cultivated in Syria (about 33, 30, 12, 10 and 5%, respectively) (ALIBRAHEM, 2006). The others are local varieties that have a limited distribution. Up to now, very few studies have been carried out to evaluate the agronomic and productive characteristics of Syrian olive cultivars (NSEIR et al., 1985;TUBEILEHefa/., 2008a,b), and very little is known about the characteristics of the oils (TUBEILEH et al., 2008b). This last aspect has become increasingly more important, since consumers are more and more sensitive about the quality of olive oil. Moreover, as a result of the large number of new olive orchards that have been planted in Syria in the last decades, an increasing amount of oil is available for export, that must meet the qualitative standards required by the international market.

More knowledge about the productive characteristics and oil quality of Syrian olive cultivars is useful for making the best choice of varieties for new olive orchards. Moreover, it is useful to determine if the oils produced by the different cultivars meet the qualitative standards required by the international market.

The aim of this study was to evaluate the fruit characteristics and oil quality of the main Syrian olive cultivars, by evaluating them in the areas where they have the largest distribution. The investigation was carried out as a part of a larger study aimed at fully characterizing the morphological, biological, agronomic and oil characteristics of the main Syrian olive cultivars (ABDINE etal, 2007). Oil characteristics were also evaluated by comparing them with the International Olive Council (IOC) trade standards for extra virgin olive oils (COI/T.15/NC no. 3/Rev. 3 - November 2008).

MATERIAL AND METHODS

The study was carried out in the three-year period 2004-06. The cultivars taken into account were: Kaissy (also known as Qaisi) and Zaity in the Aleppo area (where about 30% of Syria's olive cultivation is concentrated), Dan, Hemplasi and Souri in the Damascus area (about 3.0%), Insassy, Karamani and Sorani in the Idleb area (about 22%), Khodeiri in the Lattakia area (about 7%), Safrawi in the Hama (Mousiaf) area (about 6%) and Doebli in the Tartous area (about 13%). The areas taken into account differ with respect to environmental conditions, especially annual rainfall: 350-450 mm in Aleppo and Hama, 200250 mm in Damascus, 450-500 mm in Idleb and 800-900 mm in Lattakia and Tartous (AL IBRAHEM, 2006). The olives of all these cultivars are also used as table olives in amounts depending on the cultivar (ABDINE et al. , 2007).

In each area, 3-5 trees per cultivar were selected from germplasm collections or from private farms and labelled. Fruit samples were harvested within the normal harvesting times (October - December) in Syria: in November, for the cultivars Dan, Doebli, Hemplasi, Insassy, Karamani, Safrawi, Sorani, Souri and Zaity, and in October, for the cultivars Doebli and Khodeiri (that are harvested earlier). The samples from the labelled trees were used to determine: fruit weight (50 drupes/ tree); pigmentation (50 drupes/ tree) by using the "Jaen pigmentation index", from 0 to 7, with 0 for green olives and 7 for olives with superficial pigmentation on 100% of the epicarp and 100% pigmentation on the pulp; water content by drying the samples used for fresh weight determination in an oven until constant weight; oil content (1 sample/tree) by using a Soxhelet apparatus.

The oil was extracted from 2-3 kg of olives (2 samples/cultivar/year) using a lab hammer mill; the paste was malaxed for 30 min, then centrifuged and the oil was separated from the water and filtered through a filter plate. On the oil, acidity (ISO 660), peroxide value (ISO 3960), spectrophotometric absorbance at 232 and 270 nm (K^sub 232^ and K^sub 270^) and at 264, 268 and 272 nm (K^sub 264^, K^sub 268^, and K)) to determine ΔK = K258 - (K^sub 264^ + K^sub 272^)/2 (COI/T.20/ Doc. n. 19), fatty acid composition (COI/T.20/ Doc.n.24), sterol composition and content and erythrodiol + uvaol (triterpene alcohols) content (COI/T.20/Doc.n.lO) were determined according to the procedures indicated within parentheses.

As far as oil characteristics are concerned, the IOC trade standard values for extra virgin olive oils (COI/T.15/NC no. 3/Rev. 3 - November 2008) are reported in the tables.

As a preliminary statistical analysis of data did not show substantial year effects, data is reported in tables as means of the three-year period 2004-06±standard error.

RESULTS

The cultivars in the different environments showed notable differences in all the fruit characteristics taken into account (Table 1). Fresh fruit weight was high for the Kaissy and Safrawi cultivars, medium for Zaity, Dan, Hemplasi, Souri, Karamani, Khodeiri, Sorani and Doebli and medium-low for Insassy. The level of pigmentation was very different among the cultivars. The oil content was high in Zaity and Sorani, medium-high in Khodeiri, medium in Insassy, Karamani and Doebli and relatively low in the other cultivars.

The acidity and peroxide value of the oils of all the cultivars were very low (Table 2). K^sub 232^, K^sub 270^ and ΔK values were also low. All the cultivars had an oleic acid content around 70%, with the exception of Karamani, which had a value of about 60% associated with relatively high amounts of palmitic and linoleic acids (Table 3). The sterol composition and content and erythrodiol + uvaol content were quite different (Table 4). The Khodeiri and Doebli cultivars had relatively high Δ7-stigmastenol values, followed by the cultivars Insassy and Sorani.

The average values of all the parameters (acidity, peroxide value, absorbencies in ultra-violet, fatty acid composition, sterol composition and content, erythrodiol + uvaol content) used to evaluate oil characteristics were within the IOC trade standards, with the exception of those of the Δ-7-stigmastenol in the cultivars Khodeiri and Doebli that were higher than 0.5%, which is the maximum value allowed by IOC trade standards. It should be noted that the average values of the cultivars Insassy and Sorani were as high as 0.5% or very close to 0.5%, respectively, indicating that, also for these cultivars, in some cases (replicates) the values were higher than 0.5%. In all the oils, on average, the content of apparent ß-sitosterol (β-sitosterol + Δ-5avenasterol + Δ-5-23-stigmastathenol + clerosterol + sitostanol + Δ-5-24-stigmastathenol) was higher than 93.0%, the IOC trade standard for this parameter.

DISCUSSION AND CONCLUSIONS

The fresh fruit weight and oil content in Zaity, Sorani and Kaissy were substantially similar to values reported in the literature for the same cultivars (TUBEILEH et al., 2004, 2008a, b). The cultivar Dan showed a lower oil content than that reported by TUBEILEH et al. (2004); this difference could be due to harvesting time/ripening stage of the olives, since significant increases in oil content can be obtained by delaying harvesting (ABDINE et al., 2007).

The high-medium oil content in Zaity, Sorani, Khodeiri and Doebli indicates their high efficiency in accumulating oil in the fruit which is in agreement with the fact that these cultivars are the main ones for oil production in Syria (these 4 varieties cover about 85% of the total area cultivated with olive) (AL IBRAHEM, 2006). The medium or high fresh fruit weight, as well as the moderate oil content of the varieties Kaissy, Karamani and Safrawi, justify their use as dual purpose cultivars, with Kaissy being the main Syrian cultivar used for the production of table olives (ABDINE et al, 2007), The relatively good fruit weight of the cultivar Sorani justifies the use of the drupes also as table olives. Indeed, while most of the fruit of the variety Sorani is used for oil production, Sorani is also among the main Syrian cultivars used for the production of table olives, especially black ones (ABDINE etal, 2007). The dry environmental conditions of the Damascus area have probably contributed to determining the relatively low oil content in the cultivars Dan, Hemplasi and Souri.

As far as oil characteristics are concerned, low acidity and peroxide values were also observed in another study concerning the cultivars Kaissy, Zaity and Sorani (TUBEILEH et al., 2008b). With respect to the present work, TUBEILEH et al (2008b) reported slightly higher values for palmitic acid and lower values for oleic acid for the cultivars Kaissy and Zaity; these differences could be due to the different environmental conditions, especially temperature, and fruit ripening stage, that can affect fatty acid composition (INGLESE et al , 2009).

The Karamani cultivar had relatively low oleic acid values and high palmitic and linoleic acid values. It is known that high environmental temperatures tend to reduce the oleic acid content and increase the palmitic and linoleic acids (INGLESE et al, 2009) but, since the Idleb area is not the warmest among those considered, it seems that the observed fatty acid composition is mainly a characteristic of the variety.

The sterol composition and content as well as the erythrodiol + uvaol content differed in the cultivars; this is in agreement with the fact that these compounds are greatly dependent on cultivar (APARICIO et al, 1997; RANALLI et al, 2002; SÁNCHEZ CASAS et al , 2004; QUESLATI et al., 2009).

All the oils produced by the olive cultivars considered meet the IOC trade standards applied to extra virgin olive oils, except the cultivars Khodeiri and Doebli, which showed average of ?-7-stigmastenol values that were higher than the IOC limit. Also in some replicates of the cultivars Insassy and Sorani the values were higher than 0.5%; indeed, the reported average values were 0.5% or very close to this value. In this regard, also other measurements for the cultivar Sorani, recorded in 2008 and 2009, were between 0.4 and 0,6, and, therefore, in some cases the values were higher than 0.5% (Jbara, unpublished data). It is important to note that this value is used as an indicator of the purity of the oil, because it can indicate possible adulteration (admixtures with other vegetable oils), but some varieties naturally have relatively high contents. Apart from the cultivars taken into account in the present work, values higher than 0.5% have been observed in oils of other varieties, such as Nebbio (RANALLI and ANGEROSA, 1996), Empeltre (GÓMEZ, 2001), especially in extremely dry seasons, Cornicabra (SALVADOR etal, 1998; RIVERA DEL ÁLAMO et al , 2004), Nociara and Termite di Bitetto (LOMBARDO et al, 2004) and Colombaia (LANTERI etal, 2003; BOGGIA etal, 2005). Besides being affected by the variety, the sterol content and composition have also been reported to be affected by fruit ripening (DE LA TORRE-BORONAT et al, 1985; GUTIÉRREZ et al, 1999; SALVADOR et al , 2001) and agro-environmental conditions (STEFANOUDAKI et al, 2001; CECI and CARELLI, 2007; BEN TEMIME et al, 2008). In the hot, arid region of Catamarca in Argentina oils from Coratina showed a ?7-stigmastenol value that was higher than the IOC limit (CECI and CARELLI, 2007), whereas this value was within the IOC limit in the oils obtained in Italy (LOMBARDO et al, 2004). With reference to environmental conditions and olive ripening, the cultivars Doebli and Khodeiri showed average ?-7-stigmastenol values that were higher than 0.5% also in oils obtained from olives produced in different areas in Syria (Jbara, unpublished data) or from olives harvested in periods different from that considered in the present work (ABDINE etal, 2007). However, in 2009, a cool and rainy year, the Khodeiri cultivar showed relatively lower values (Jbara, unpublished data). In other studies, values exceeding the upper limits established by the IOC standards were also found for other sterol compounds, such as campesterol (RIVERA DEL ALAMO et al, 2004).

The overall results regarding the oil characteristics are very important because of the increasing amounts of Syrian olive oil that will be available for export in the coming years.

It should be noted that the different cultivars were studied in order to obtain information about characteristics of the olives and the olive oils obtained in Syria, The study considered all the main Syrian olive varieties in the areas where they are mostly located. The olives were harvested according to the normal local practices. The different cultivars were cultivated in different environments and the ripening stage of olives was not uniform. Therefore, the results reported are dependent on the cultivar and could also have been affected by the differences in the environmental conditions in the different areas considered as well as the ripening stage of the olives.

In conclusion, the results of the study show that good fruit and oil can be produced with the main olive cultivars cultivated in Syria; the olive oil produced meets the IOC standards. One concern regards the Δ-7-stigmastenol content; some cultivars had values higher than 0.5%, the maximum value established by the IOC trade standards. The results of this study should be considered when updating the international rules/standards regarding the trading of olive oil.

ACKNOWLEDGEMENTS

The present study is related to the activities of the cooperation project 'Technical Assistance for the Improvement of Oil Quality in Syria" (2004-2007), funded by the Italian Ministry of Foreign Affairs, implemented by the International Centre for Advanced Mediterranean Agronomic Studies - Mediterranean Agronomic Institute of Bari (CIHEAM-IAM Bari, Italy) and by the Syrian General Commission for Scientific Agricultural Research (GCSAR). It is a re-elaboration/extrapolation of a paper presented by JBARA et al. (2006) at Olivebio teq 2006 - Second International Seminar on 'Biotechnology and Quality of Tree Products Around the Mediterranean Basin' and a work on the characterization of the main Syrian olive cultivars published within the above -cited project (ABDINE et al, 2007).

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Revised paper received April 15, 2010 Accepted May 28, 2010