Physical and chemical characteristics of five Turkish olive ( Olea europea L . ) varieties and their oils By

Aceitunas de Turquía de cinco variedades (Gemlik, Kilis, Uslu, Tirilye y Ayvalik) así como sus correspondientes aceites obtenidos por métodos clásicos fueron usados en este estudio. En las aceitunas se determinó la composición proximal (humedad, contenido graso, proteína, cenizas, fibra, y extracto soluble en alcohol), el contenido en minerales y en fenoles. En el caso de los aceites se determinó la composición en ácidos grasos, acidez, insaponificable, índices de Yodo y de saponificación, densidad e índice de refracción. El contenido en aceite de las muestras fue muy variable oscilando entre 17.7 y 43.5% y el de fibra entre 3.6 y 7.0%. El contenido en minerales de las aceitunas fue excelente destacando el elevado contenido en Ca, Fe, K, Mg, Na y P. Los contenidos de K, Na y P fueros superiores en las aceitunas de la variedad Gemlik. Respecto a los aceites los rangos de concentración encontrados para los principales ácidos grasos fueron: ácido oleico entre 65.71 y 83.58%; ácido palmítico entre 8.1 y 15.2%, ácido linoleico entre 3.5 y 15.5% y ácido esteárico entre 2.0 y 3.6%. El contenido en compuestos fenólicos, expresados como equivalentes de ácido gálico y catéquico, fue muy variable. Se encontraron cantidades entre 22.5 y 97.1 mg/kg y entre 12.3 y 98.7 mg/kg cuando se expresan como ácido gálico y catéquico, respectivamente, correspondiendo los contenidos menores a los de la variedad Kilis.


INTRODUCTION
The olive tree (Olea europea L.) grows in a subtropical climate as a traditional main crop, familar in Mediterranean countries.It probably originates from Mesopotamia and has been cultivated from many centuries in southern European countries bordering the Mediterranean and in North Africa (Karleskind and Wolff, 1998;O'Brein, 1998;Murkovic et. al., 2004).
In ancient times, the Mediterranean people considered olive oil not only an excellent food but also a healing agent.During the past four decades a renewed interest in the nutritional and health aspects of olive oil has been generated.Olive oil is a key component of the traditional Mediterranean diet, which is believed to be associated with a relatively long life in good health.Virgin olive oil is unique among other vegetable oils because of the high level of particular phenolic compounds, to which, together with the high content of unsaturated fatty acids, the health benefits of olive oil are attributed (Kiritsakis and Markasis, 1984;Visioli and Galli, 1998).
An abundance of oleic acid, a monounsaturated fatty acid, is the feature that sets olive oil apart from other vegetable oils.The Mediterranean diet includes the consumption of large amounts of olive oil, which contains high amounts of phenolic substances (Aparicio and Luna, 2002;Garcia et al., 2003;Murkovic et al., 2004).Olive oil phenols also contribute to the characteristic taste and the high stability of olive oil against oxidation (Tsimidou, 1999).The most important classes of phenolic compounds in olive fruit include phenolic acids, phenolic alcohols, flavonoids and secoiridoids (Vinha et al., 2005).
The aim of this investigation was to determine the physical and chemical properties, mineral PHYSICAL AND CHEMICAL CHARACTERISTICS OF FIVE TURKISH OLIVE (OLEA EUROPEA L.) VARIETIES AND THEIR OILS contents, fatty acid composition and total phenol contents of five different olive varieties.

Materials
Olive fruits were collected from five different locations (Balıkesir, Bursa, Kahramanmaras ‚ , Manisa and Tekirda ˘) in south and west Anatolia in the year 2003.In each location, the chosen cultivars were those predominating in the respective area.The samples were collected during the period when olives are usually harvested for oil production.For each sample (about 1000 g) of olive fruits were manually collected from the same three olive trees, and kept at +4 °C by using.

Methods
The average weight of an olive and its pit were determined by measuring the weights of 30 olive fruits and their pits.The chemical and physical properties (moisture, fruit and pit weight, crude protein, crude oil, crude fiber, crude energy, ash, pH, and alcohol soluble extract, free fatty acids, iodine value, peroxide value, saponification number, unsaponifiable matter and refractive index) were analyzed according to AOAC (1984AOAC ( , 1990)).The amounts of oil used for the determination of free fatty acids and peroxide values were 2.0 g and 5 g, respectively.The oil was extracted with diethyl ether (50 °C) in a Soxhlet apparatus.The extract was evaporated in vacuum.The lipid extract was collected in a flask.The extracted lipid was weighed to determine the oil content and stored under nitrogen at 4 °C for further analyses.About 10 g of the oil was heated under reflush and saponified with 5 ml of ethanolic potassium hydroxide solution (20 % w/v) for 2 h.The unsaponifiable matter was extracted three times with 15 ml of petroleum ether, and the extracts were combined and evaporated in a rotary evaporator at 40 °C under reduced pressure.The unsaponifiable residue was weighed.For peroxide value, about 5 g of olive oil was dissolved in a mixture of acetic acid / chloroform (3:2 v/v), and a saturated solution of KI (1 ml) was then added.The liberated iodine was titrated with sodium thiosulphate solution (0.05 M) in the presence of starch as indicator.For the free oil acidity, a known weight of olive oil was dissolved in a mixture of diethyl ether/ethanol (1:1 v/v).The mixture was titrated with potassium hydroxide in methanol (0.05 M) in the presence of phenolphthalein as indicator.

Determination of fatty acids
Fatty acids were derivatized using the boron trifluoride method (Hıs ‚ ıl, 1988).The working conditions of gas chromatography were as follows.
The fatty acid composition for walnut olive samples was determined using a modified fatty acid methyl ester method as described by Is ‚ıl (1998).The oil was extracted three times for 2 g air-dried seed sample by homogenization with petrolium ether.The oil samples (50-100 mg) were converted into fatty acid methyl esters (FAME).FAME (5 μl) were analyzed using a Varian 2100 chromatograph on a fused silica capillary column MN FFAP (10 % diethylene glycol succinate, 50 m ϫ 0.32 mm i.d.; film thickness 0.25 μm), under the following temperature programme: 90 °C (7 min), 5 °C /min to 240 °C (15 min).The flow rate of nitrogen, used as carrier gas, was 6 mL/min.Temperature of both injector and flame ionization detector was 225 °C.The fatty acids were converted to their methyl esters by heating them in 10% BF 3 -methanol.Commercial mixtures of fatty acid methyl esters were used as reference data for the relative retention times (AOCS, 1990).Results are given as mean values of two replicates.

Determination of mineral contents
About 0,5g of dried and ground olive fruits were put into a (burnig) cup with 15 ml of pure HNO 3 .The sample was incinerated in a MARS 5 microwave oven at 200 °C.Distilled deionized water and ultrapure commercial acids were used to prepare all reagents, standards, and olive samples.After the digestion treatment, samples were filtrated through whatman No 42.The filtrates were collected in 50 ml Erlenmayer flasks and analyzed by ICP-AES.The mineral contents of the samples were quantified against standard solutions of known concantrations which were analyzed at the same time.(Skujens, 1998).

Determination of total phenol content of olive oil extracts
About 100 g of oil was extracted three times with 500 ml of methanol (water: methanol; 60:40) (Tsimidou et al., 2005).The total phenols in the oil extracts were measured by the Folin-Ciocalteu assay (Tsimidou et al., 1999).The measurement was carried out at 765 nm via UV-spectrophotometer (Shimadzu).Results were expressed as mg of gallic acid and cathechin equivalent in one kg oil.Yields of the extracts were based on differences in weight (Singleton and Rossi, 1965).

Statistical analysis
Results of the research were analyzed for statistical significance by analysis of variance (Düzgünes ‚ et al., 1987).The data from the experiment were subjected to ANOVA using a randomized complete block design with statistical analysis system-ANOVA procedure (Minitab, 1991).

Weight of fruits and pits
Differences between the weight of fruits and pits were significant (p Ͻ 0.01) for all cultivars Table 1.The highest fruit weight was established in the Ayvalık variety.The pit weight of Uslu variety was determined as 0.630 g.Akpınar and Bas ‚og ˘lu (1999) reported that the fruit weight of edible oil fruit was 3.5 g-3.9 g.In other studies, these values were determined as 2.5-4.1 g (Yazıcıog ˘lu, 1966), and 3.3-4.2g (Kılıç, 1986), 1.7-3.6 g (Anonymous, 2003) for oil olives.The pit weights according to literature ranged from 0.4 -0.6 g (Akpınar and Bas ‚og ˘lu, 1999), 0.3-0.4g (Kılıç, 1986) and 0.5-0.8g (Balatsouras et al., 1982) for some table olives.Anon., (2003) reported the pit weight of edible olive oil fruits as ranging from 0.3-0-5 g. Results were similar to the values found in the literature .Differences may be due to soil characteristics, fertilization and cultivar differences.

Mineral Contents of olive fruits
The mineral contents of several olive varieties were determined by ICP-AES (Table 3) and found to be excellent.Olive fruits have advantages over fruits such as terebinth, (Özcan, 2004).All olive varieties were found to be rich in K, P, Ca, Na, Mg and Fe.Also, K, Na and P contents of Gemlik varieties were found higher than those of other varieties.According to the variance analysis, olive varieties had a significant effect on B, Cu, K and Mg (p Ͻ 0.01) and on Li (p Ͻ 0.05) (Table 3).Some mineral contents such as Ca, Fe, K, Mg, P and Zn of olive fruits varied between 481 mg/kg to 1176 mg/kg, 113 to 283 mg/kg, 4724 to 11442 mg/kg, 119 to 275 mg/kg, 605 to 1187 mg/kg and 4.9 to 14.4 mg/kg, respectively (Table 3).Manouskas et al. (1978) reported that fresh olive fruits contained Na (32.0 ppm), K (4571.9ppm), Ca (331.5 ppm), Mg (124.9 ppm), Mn (1.3 ppm), Fe (12.2 ppm), Zn ( 7  ppm), Cu (0.1 ppm) and P (511.3 ppm).Results were high compared to literature values.This situation is due to the sample analysis which is not done according to fresh basis.

Chemical and physical properties of olive oils
The characteristics of the main chemical properties of olive oils extracted from all varieties are shown in Table 4.According to variance analyses, all olive varieties had significant amounts of free fatty acid, iodine value, saponification value, unsaponifiable matter, refractive index, specific gravity (p Ͻ 0.01) and peroxide value (p Ͻ 0.05) (Table 5).
Our results are similar in fatty acid composition, when compared to the values in the literature .The fatty acid composition in oils is affected by species, genetics, variety, growing conditions, locality, climatic conditions and postharvest treatment (Kiritsakis and Markakis, 1984).

Total phenol contents of olive oils
Table 6 presents the total phenol contents of Gemlik, Kilis, Uslu, Tirilye and Ayvalık olive oils.The content of total phenols in the oil extracts was measured by the Folin Ciocalteu assay (Tsimidou, 1999) and expressed as catechic and gallic acid equivalents.Differences between total phenol contents of oils were significant at p Ͻ 0.01 (Table 6).
The total phenol contents as gallic and catechic acid equivalent in all oil samples ranged from 22.5 to 97.1 mg/kg and 12.3 to 98.7 mg/kg, respectively.While the phenol values of oils from the Uslu and Tirilye varieties were found similar, the phenol content of oil from the Gemlik variety was higher.The phenol contents of oil from the Ayvalık variety was found higher than the Kilis samples.Montedoro et al. (1992) reported that the total phenol contents of Italian olive oils were found between 50 to 1000 ppm and classified as 50-200 ppm (low), 200-500 ppm (middle) and 500-1000 ppm (high).Our results can be classified as low (50-200 ppm) according to Montedoro et al. (1992).The Total phenol content of commercial olive oil is about 400 mg/kg as caffeic acid equivalent (Garcia et al., 2003).The total phenol contents of oils were effected by maturation, nature of the cultivar and geographical origin (Vinha et al., 2005).Means with different superscript letters differ significantly (n ϭ 3).

Table 1 Weight of olive fruits and pits Cultivars Fruits (g) Kernels (g)
aMeans with different superscript letters differ significantly (n ϭ 30).