Characterizing of Oil Quality and Fatty Acid Profiles of Old Olive Trees in Palestine

: Olive growing in Palestine plays an important role at social and economic levels. Nevertheless, the quality of olive oil produced in the country has not been fully addressed. This study examined oil content, peroxide values, acid values, fatty acid profile, and total phenolic content for old olive trees located in different climatic regions in Palestine during the years 2008-2010. Oil content was determined using both Soxhlet and Abencor systems. Acid and peroxide values were determined using standard methods. Total phenolic content was determined using the Folin-spectrophotometric method. Gas chromatography was used to analyze the main fatty acids found in olive oil e.g., palmitic, palmitoleic, stearic, oleic, linoleic. Different ratios indicating olive oil quality were also determined e.g., sum ratio of unsaturated fatty acids to the sum of saturated fatty acids; ratio between the sum of monounsaturated fatty acids to the sum of polyunsaturated fatty acids, and the ratio between the oleic to linoleic fatty acids. Significant differences were found between geographic regions for the overall studied oil parameters. Wide variation ranges were obtained for fatty acids in the different West Bank locations in the three years. The major fatty acids in the olive oil samples were found to be oleic, palmitic, stearic, linoleic, and palmitoleic acids. The oil samples were found to contain more oleic acid and less linoleic and linolenic acids that is, more monounsaturated than polyunsaturated fatty acids. Total phenolic content was found to range from 125.0-978.0, 207.4-763.8, and 103.0-747.6 mg/kg in 2008, 2009, and 2010, respectively. The acidity percentage was in the range of 0.10%-1.05%, 0.11%-1.29%, and 0.10%-1.91% in 2008, 2009, and 2010, respectively. Peroxide values ranged from 2.26-13.1, 2.94-14.95, and 2.49-17.21 in 2008, 2009, and 2010, respectively. oil ） ; linolenic acid （ C18:3, a polyunsaturated omega-3 fatty acid that makes up 0-1.5 ％ of olive oil ） ; stearic acid （ C18:0, a saturated fatty acid that makes up 0.5 ％ -5 ％ of olive oil ） ; palmitic acid （ C16:0, a saturated fatty acid that makes up 7.5 ％ -20 ％ of olive oil ） . phenolic compounds, C18:0, C18:1 cis , C22:0, oleic acid, and MUFA.

product 4 . The primary olive productive areas are located in the western and northern West Bank the western slope of the mountains that is characterized by a Mediterranean climate. The areas with the largest groves are in Jenin, Nablus, Tulkarem, and Ramallah 5,6 .
Old olive groves and individual olive trees can still be found in Mediterranean, semi-arid and even arid climates in Palestine. A survey of traditionally-cultivated olive groves showed a wide distribution of orchards of landrace cultivars. Trunk circumference is usually a reference to estimate tree age. Some of the surveyed trees were found to have a circumference of over 4 m and are ca. 1000 years or older 7 .
Olive oil, and its main derived product, experienced an increase in popularity due to its organoleptic characteristics that are associated with health benefits 8 . Fatty acid composition varies widely in vegetable oils. Several studies have shown the dietary importance of fatty acid composition in olive oils. Fatty acid composition has been shown to influence the stability of oils, and polyunsaturated fatty acids have been found to contribute to the rancidification of several oils 9 . Fatty acid composition has been found to be responsible for the odors and flavors associated with oil quality 10 .
The approved limits of some fatty acids were published by the European Union 11,12 and the International Olive Oil Council as well as previously discussed by other researchers 13 . Respect of these limits does not characterize olive oil particularly extra virgin and virgin as currently defined .
Additionally, fatty acids are associated with oil health beneficial relevance, mainly monounsaturated fatty acids, and to minor constituents such as tocopherols and phenolic compounds 14 . The fatty acid composition of olive oil varies widely depending on the cultivar, maturity of the fruit, genotypes, altitude, climate, and several other factors 15 . The major fatty acids in olive oil are 16 : Oleic acid C18:1, a monounsaturated omega-9 fatty acid. It makes up 55 -83 of olive oil ; linoleic acid C18:2, a polyunsaturated omega-6 fatty acid that makes up about 3.5 -21 of olive oil ; linolenic acid C18:3, a polyunsaturated omega-3 fatty acid that makes up 0-1.5 of olive oil ; stearic acid C18:0, a saturated fatty acid that makes up 0.5 -5 of olive oil ; palmitic acid C16:0, a saturated fatty acid that makes up 7.5 -20 of olive oil .
Some studies were carried out with the aim of characterizing particular productions of olive oil, which have given great importance to the fatty acid profile. Other studies investigated fatty acid profiles and olive oil quality parameters e.g. acid value, peroxide values, sterol content, phenolic content from various geographic regions and different olive cultivars 17 19 .
Several researchers tried to correlate the geographical origin to the fatty acid composition in olive oil. Garcia and Lopez 20 investigated the possibility of distinguishing among extra virgin olive oils produced in different regions of Spain, Italy and Portugal based on their fatty acid content. Tsimidou and Karalostas 21 classified Greek virgin olive oils according to multivariate analyses of the fatty acid composition of the oils. Other researchers Stefanoudaki et al. 22 studied the characterization and authenticity of virgin oils extracted from the olive varieties Coratina Italy , Picual Spain , and Koroneki Greece by matching sensory, physical, chemical, and compositional data within their fatty acid composition.
The objective of the current work is therefore to investigate fatty acid profiles and oil quality parameters acidity percentage, peroxide value, and total phenolic content obtained from old olive trees in Palestine over three consecutive years 2008-2010 as affected by different geographical regions. This current work has not been previously investigated.

Tree selection
In this research, 15 sites inhabiting old trees in Palestine were chosen from the south to the north. The selected sites include: Sourief, Bait Jala, Bait Reema, Kufr Ein, Beit Anan, Bediah, Kufr Al Diek, Azzoun, Sinieria, Zaita, Bieta, Dier Al Gosoun, Saida, Kufr Ra ai, and Berqien. From each site, 10 trees were selected according to the trunk perimeter criteria consisting of 150 cm and above.

Site and tree identi cation
Each selected tree in each site was identified by a tree code, composed of 11 numbers xxxyyyyzzz/n where xxx represents the province, yyyy represents the village in each province and zzz represents the farmer s name in each village, while n is a serial number representing the tree s number in each field. The following information identified GPS marking for coordinates, tree height, trunk perimeter, and pressure.

Tree sampling and analysis
During the harvest, each selected tree was sampled as follows: around 2 kg of olive fruit was sampled from each tree.

Olive oil analysis
One kg of olives from the 2 kg olive sample was taken to a laboratory and kept overnight in a refrigerator at 4 . The fruits were crushed electric hammer crusher, 4 mm sieve, MC2, Seville, Spain . Uniform paste was divided with about 300 g used to determine water and oil content and 700 g were used for mechanical oil extraction ABENCOR system, MC2, Seville, Spain . The paste was mixed with 300 ml tap water for 20 min at 30 , then centrifuged for 60 sec at 3500 rpm. Liquids were placed in a cylinder until phase separation. Oil was decanted for chemical analyses and kept in a glass bottle at 15 until analysis.

Determination of water and oil content
In determining water and oil content, the paste was weighed and placed in a drying oven for 48 hr at 105 . It was then weighed again. Water loss was calculated. Weighed dry paste was placed in a Soxhlet apparatus for 6 hr under hexane for oil extraction. The organic matter was weighed and oil content calculated.

Determination of free fatty acids acidity levels
Free fatty acids FFA , expressed as the percentage of un-bonded oleic acid of the total fatty acids, was determined by dissolving a 2.2 g oil sample in 15 ml EtOH-diethyl ether mixture with addition of 1 phenolphthalain indicator, then titration with 0.01N ethanolic KOH-until pinkish color, according to the EU official method 23 .

Determination of peroxide value
The peroxide number, millimoles of active oxygen in one kg of oil was determined according to the EU official method 23 . About 1.2 mL of oil was dissolved in 25 mL solvent mixture Acetic acid:Iso-octane 3:2 ratio with the addition of 250 μL saturated KI solution. The reaction was stopped after 1 min by adding 250 μL of 1 starch solution. The mixture was then titrated with Na 2 S 2 O 3 0.01N until the dark brown color of the original mixture disappeared.

Determination of total phenolic content
For determining the total content of polyphenol compounds in oil samples, 275 μL oil were dissolved in 500 μL hexane then 350 μL methanol 60 was added. Strong vortex emulsifies the mixture. After 3 min of centrifugation at 14000 rpm, the lower methanolic phase that contain phenolic compounds was kept. The lipidic phase underwent a second methanolic extraction where 300 μL hexane was added to the combined extract to remove the remain-ing oil.
The content of total polyphenols in the extract was determined through a Folin-Ciocalteu Reagent FCR , using a modified method 24 . To 200 μL extract, 3 mL water and 250 μL FCR were added and incubated for 5 min. Then, 750 μL of Na 2 CO 3 20 was added and incubated for 10 min. Finally, 950 μL water was added and incubated for another 10 min, the absorbance at 735 nm was measured using a spectrophotometer. Total phenolic content is expressed as mg Catechin per kg oil.

Determination of fatty acids of the oil samples
Methylated fatty acids FAME profile was determined according to the IOC official method 25 using Gas Chromatograph model 7890A Agilent technologies, USA on a DB23 capillary column 60 m 0.25 mm, 0.25 μL film; J&W Scientific, Folsom, CA, USA and FID Flame ionization detector . Approximately 0.1 g oil was dissolved in 2.0 mL nheptane GC grade, Merck with 0.2 ml methanolic KOH 2N . After strong vortex and 30 sec wait, the upper fraction containing FAME was collected and analyzed. Peak identification and retention times were compared to external standards FAME mix C8-C24 .

Environmental measurements
Environmental information collected from the data environmental database included aspect, slope, altitude, lithology, mean day temperature in January, mean day temperature in August, maximum temperature in June, minimum temperature in January, and precipitation.

Statistical analysis
Three samples of each treatment were independently analyzed in each sampling. All the determinations were carried out in triplicate. All statistical analyses were carried out using SAS SAS Institute Inc., Cary, USA, Release 8.02, 2001 . Mean comparisons were carried out using the GLM procedure, treating main factors separately using one-way analysis of variance ANOVA . Differences were considered significant if P values were lower than 0.05. The Bonferroni procedure was employed with multiple t-tests in order to maintain an experiment-wise of 5 . Pearson correlations were calculated to test the relation between quality parameters and fatty acids in olive oil. The NOMISS option was used in order to obtain results consistent with subsequent multiple regression studies.

Results and Discussion
Olive fruit was obtained from 15 geographical locations in West Bank ranging from northern to middle and southern West Bank. In Palestine, three climatic zones can be recognized including the Mediterranean zone in the western slopes of the mountains running north-south, the semi-arid the top of the eastern slopes and arid zones in the middle and the bottom of the eastern slopes. In general, the local climate is characterized by dry summers with rainy and cold winters. While annual precipitation in the semi-arid and arid environments is low 200-300 and 100 mm/year, respectively , it is more diverse in the Mediterranean region. There, topography affects annual rainfall which ranges from ca. 350 mm/year in some districts to more than 800 mm/year. In addition, summer and winter temperature regimes differ along north-south and westeast transects. Winters are harsher in the mountains of the north and east while the coastal plain is characterized by relatively warm winters 8 . The average annual temperature in the inner plain is higher but relative humidity decreases with increasing distance from the Mediterranean Sea towards the east. Traditional olive groves in Palestine are mainly concentrated in the mountainous areas, inland and southern districts of the region, in areas with more than 350 mm rainfall/year 7 .

Percentage of oil and water content in olive fruit
Results showed that the percentage of oil content using the Abencor system in 2008 was not significantly different among the various locations in West Bank, with the exception of Sourief which is significantly lower than other locations. In 2009 and 2010 on the other hand, significant differences in oil content percentage were observed between some locations in West Bank as shown in  26 . In 2008 on the other hand, the lowest percentage of oil was found in Sourief while the highest percentage was found in Sinieria. In 2009, the amount of olive fruit on olive trees was so low that very modest amounts of olive oil were produced that year, this explains why olive oil was only collected from six regions in the West Bank as shown in Table 1 It is interesting to compare oil content obtained from the two extraction methods chemical extraction method/ Soxhlet compared to the mechanical/Abencor extraction method . Results showed that Soxhlet is superior in extracting olive oil from olive fruit containing the highest oil content of 33.4 compared to 27.8 for the Abencor extraction system. Additionally, the oil content of the Soxhlet method ranged from 20.  Table 1 .

Total phenolic content TPC of olive oil samples
Results in Table 2, show that the total phenolic content of olive oil is affected by geographical location, where it was found that there are significant differences in total phenolic content of olive oil among the locations in all years. The maximum TPC value was found for oil samples Phenolic compounds are important secondary metabolites present in olive oil. They are a complex class of chemicals including a hydroxyl group on a benzene ring. Phenolic compounds are defined based on metabolic origin and these substances derive from the shikimate pathway and phenylpropanoid metabolism 26 . Phenolic compounds are a complex mixture of compounds with different chemical structures obtained from oil by extraction with methanolwater. Phenolic compounds are related to the stability of oil in addition to its biological properties. Most phenolic compounds are found in nature in a conjugated form 27 . Virgin olive oil contains at least 30 phenolic compounds. The total phenolic amount and composition of olive oil varies from 100 to 1000 mg/kg. The TPC of olive oil samples in this study was found to range from 201.7-607.6 mg/kg which is in accordance with the literature value 27 .
Many studies were conducted on TPC of olive oil samples from different regions. Dagdelen 28 studied phenolic content of virgin olive oil obtained from three different locations in Turkey. The total phenolic content was found to reach between 159.99-189.64 mg gallic acid equivalent/ kg. Houshia and Qutit 27 measured the total concentration of polyphenol in some samples of Palestinian olive oil and results showed that TPC in olive oil ranges from 150-300 mg/kg 27 . Eid and EL-Sayed 29 characterized virgin olive oil from four olive oil cultivars in Egypt during two successive seasons 2010/2011 and 2011/2012. Total polyphenols mg caffeic acid/kg was found to be in the range of 60.40-174.20. Dabbou et al. 30 studied the antioxidant capacity of phenolic extracts of four Tunisian olive oils and total phenol content ranged between 396-652 mg kg 1 .
The amount of olive oil phenolic compounds, such as oleuropein derivatives is of primary importance when evaluating its quality, as these natural antioxidants improve oil resistance to oxidation and are responsible for its sharp bitter taste 31 33 . The pharmacological interest of olive phenolic compounds is also well-known 34, 35 .

Acidity percentage and peroxide values of olive oil
samples Acidity percentage as well as peroxide value were determined for the olive oil samples from different locations harvested in 2008, 2009 and 2010 Table 2 . Regarding the acidity percentage for olive oil samples investigated in this study, results showed that olive oil samples obtained in 2009 were not significantly dissimilar between different regions, while in 2010, oil samples from Beit Anan were significantly higher than all other samples from different regions see Table 2 . In 2008 on the other hand, results showed that two categories of geographic regions were observed where the acidity percentage of the first category was significantly higher than the other indicated by capital letters A and B . The highest acidity percentage values in 2008 were 0.42 for samples obtained from Sinieria while the lowest value was obtained from samples in Sourief 0.17 . The acidity percent in 2009 ranged from 0.30 -0.43 , while in 2010 it ranged from 0.26 -1.14 .
The acidity of olive oil indicates the percentage of oleic acid in an oil and is the primary indicator of its quality which should be less than 0.8 in extra virgin olive oil 36 . There are many factors that affect the acidity percentage of olive oils e.g. geographic region, health status of olives, harvesting technique 37, 38 , as well as storage time and conditions 31,32 . Olive collection also has a profound effect on the quality of the resulting oil, with hand picking serving as the best technique. If the collection is delayed, the natural fall of the fruit takes place and a series of alterations deteriorate the quality of the oil, particularly its acidity 37 . Free oleic acid in the oil can increase if lipase enzymes act. The process can be intensified if the olive suffered a cellular injury: insect attack, injury during collection and transport, as well as poor agricultural and environmental status. The lipase enzymatic activity is also favored by fairly high temperatures, between 30 and 40 39 .
Olive oil is classified as extra virgin when free acid content is less than 0.8 and is classified as virgin if its acidity is between 0.8 -2.0 . Olive oil samples analyzed in our study were found to be of extra virgin quality with an acidity percent reaching less than 0.8 while only one sample was found to have an acidity percentage higher than 0.8 which was from Beit Anan in 2010 1.14 .
Peroxide values expressed as mequivalent O 2 per kg were also determined for the oil samples Table 2 . In 2008, results showed that peroxide values were not significantly different between the various locations indicated. In 2009 and 2010 significant differences in the peroxide values were observed between the various locations. In 2009, the highest peroxide value was found to be 8.6 from Bediah while the lowest value was 5.4 from Beita. On the other hand, in 2010, the highest peroxide value was 12.1 from Beit Anan while the lowest value was 3.4 from Sourief.
Results of this study showed a wide range of peroxide values for oil samples from different regions and different harvesting years, where the highest value and lowest values were identified as 12.1 from Beit Anan in 2010 and 3.4 from Sourief in 2010 , respectively.
Olive oil with a peroxide value of less than 20 is classified as extra virgin according to standards established by the International Olive Oil Council. This indicates that all samples investigated in this study are of extra virgin olive oil quality.
A very low peroxide value is desirable. The starting point of the peroxidation process takes place during oil pressing and is affected by storage conditions of the oil 31 . The peroxide content PV , measured in milliequivalents of active oxygen per kilogram determines the initial oxidation of the oil. The peroxidation of the oil primarily arises due to the oxidation process, high temperature, and visibility to light. Contact with metal surfaces can also cause faster oil oxidation. The lower the peroxide value the longer the oil will retain its shelf life and will delay the possibility of rancidity. A high peroxide value usually indicates poor processing and that the quality of the oil is low. Setting a low peroxide value standard for olive oil means that it will be more stable and if correctly-stored, shelf life will be extended. High peroxide levels indicate that oil has been damaged by free radicals and will give rise to aldehydes and ketones that can cause oil to smell musty and rancid. These reactions are accelerated by heat, light, and air oxidation . Oxida-tion is a natural process. It occurs more slowly, however, in extra virgin olive oils VOOs with the highest levels of oleic acid and polyphenols 39 .
The quality indices free acidity, peroxide value, TPC of the obtained olive oils were analyzed to obtain a more complete characterization of these oil samples. Results revealed that all the analyzed VOOs were classified in the extra virgin category according to the regulated physicochemical parameters.
The major component of olive oil is a mixture of fatty acids. The fatty acid composition of olive oil varies widely depending on the cultivar, maturity of the fruit, altitude, climate, and several other factors 15 . The major fatty acids in table olives are oleic, palmitic, stearic, linoleic, and palmitoleic acids 40 . Because table olives are mainly composed of MUFAs, the consumption of table olives can prevent and reduce the risk of cardiovascular diseases, regulate cholesterol levels, stimulate transcription of LDL-cholesterol receptor mRNA and reduce breast cancer risk 15 .
Several studies have shown the dietary importance of fatty acid composition of lipids. A diet rich in monounsaturated fatty acids may reduce low-density lipoprotein cholesterol and total cholesterol without altering beneficial high-density lipoprotein cholesterol levels 41 . Fatty acid composition has been shown to influence the stability of oils, and polyunsaturated fatty acids have been found to contribute to the rancidification of several oils 42,43 . Fatty acid composition has also been found to be responsible for odors and flavors associated with oil quality.  Table 3. The range of palmitic acid content in 2008 was 11.9 -14.6 for olive fruits collected from Kufr Aldiek and Kufr Ein, respectively, while it ranged from 12.2 -14.9 for 2009 olive oil samples from Bait Jala and Bediah, respectively. In 2010 on the other hand, the highest palmitic acid content identified was 14.9 for Saida and the lowest was 10.9 for Beit Anan. The range of palmitic acid content in the three years from the 15 locations was 10.9 -14.9 , and this concurs with the literature values of palmitic acid 7.5-20 of olive oil .
The amount of palmitic acid obtained in our study is consistent with many other studies 12,40,44 . Palmitic acid C16:0 is the principal saturated fatty acid in olive oil that is responsible for its figeability at low temperatures. There are few exceptions as palmitic acid content depends heavily on genetic factors. Palmitic fatty acids, important for the nutritional properties of olive oil, showed a crucial rule in the characterization of olive oils.
Stearic acid C18:0 content was also determined for olive oil samples and results showed that this content is not significantly different in the various locations in 2009, while significant differences in the content of stearic acid were observed among locations in 2008 and 2010. The stearic acid content ranged from 2.2 -4.5 in oil samples from Kufur Ein in 2008 and Dier Al Gosoun in 2008, respectively Table 3 . The content of stearic acid in oil samples analyzed in this study agrees with the literature values 0.5 -5 of olive oil .
Results showed that the most abundant content of this fatty acid was measured in oils from the years 2010 and 2008 as compared to 2009.  Table 4. Results showed significant differences in the content of trans palmitoleic acid among locations indicated by capital letters. In 2008, the range reached 0.10-0.56, while in 2009 and 2010 the range reached 0.08-0.12, and 0.09-0.13, respectively. Regarding cis palmitoleic acid C16:1 , significant differences were also observed in their content among the various locations indicated by capital letters in Table 4. Comparing the amounts of cis and trans palmitoleic acid C16:1 , it is obvious from the results that cis content is higher than the trans isomer of palmitoleic acid C16:1 ; the range of cis is 0.35 to 1.12 compared to 0.08-0.56 for trans isomer for pooled samples from all locations in the three years.
Most of the natural unsaturated fatty acids in edible oils are non-conjugated acids with a cis structure. Meanwhile,  natural TFAs account for only a very small fraction of natural unsaturated fatty acids. The cis-trans isomerization of unsaturated fatty acids in edible oils is not expected in most cases because an excessive intake of trans fatty acids TFAs has been associated with the increased risk of coronary heart disease CHD , sudden death, diabetes mellitus and increased markers for systematic inflammation 45 . The sum of cis and trans palmitoleic acid C16:1 is shown in Table 5. The range of the sum was found as 0.52-1.23, 0.58-0.86, 0.48-0.82, for 2008, 2009, and 2010, respectively. The results of this study are in agreement with the literature in terms of palmitoleic acid content of olive oil which ranges from 0.3 -3.5 . In a study of olive oil from Lebanon the palmitoleic acid percentage ranged from 0.3 -3.5 46 . In another study, the range was from 0.7 -8.1 47 . This difference in percentage of palmitoleic acid in the olive oil samples from different regions and countries can be attributed to many factors, and in some instances the percentage of palmitoleic acid differs from one sample to another. The percentage of palmitoleic acid is influenced by the olive variety, production zone, climate and stage of maturity of the drupes at the time of collection 48 .
3.7 Content of trans and cis oleic acid C18:1 of olive oil samples Trans and cis oleic acid C18:1 contents of olive oil samples were also determined Table 6 . Table 6 revealed that cis oleic acid content is lowest in Saida 63. 4 and increases in other regions, reaching 68.2 in Kufr Al Diek in 2008. In 2009, its lowest content was found to be 66.6 in Zaita and the highest content reached 69.3 in Bait Jala. In 2010 on the other hand, the range of cis oleic acid was 60.4-68.2.
Trans oleic acid was also found to be significantly different between the olive oil samples collected from different locations under investigation; in 2008 the lowest value was found in Kufr Al Diek 1.3 and the highest in Kufr Ein 3.0 . In 2009 and 2010, the range of trans oleic acid was 1.5-2.1 and 0.5-1.8, respectively. As expected, the amounts of trans oleic acid is very minor compared to cis oleic acid.
The sum of cis and trans oleic acid C18:1 is shown in Table 7. The range of the sum was found to be 65.0-69.6, 68.4-70.7, 62.1-68.9 for 2008, 2009, and 2010, respectively. The results of this study are in agreement with the literature concerning oleic acid composition of olive oil which ranges from 55 -83 as well as previous investigators that documented a range of 64.4 -68.9 for oleic acid 44,49 .
acid in olive oil and is associated with its high nutritional value and oxidative stability 50,51 . An olive variety is considered to have a high oleic acid content if C18:1 is about 65 and above 52 . In the present study, most of the samples studied have an oleic acid percentage higher than 65 which is categorized as a high oleic acid content.
In particular, high levels of MUFAs mainly oleic acid , which have health benefits and are important for human nutrition, are among the major components of the Mediterranean diet. They also play an important role in the nutritional value of table olives 16,44,49 . Polyunsaturated fatty acids like linoleic C18:2 , and linolenic C18:3 were present in olive oil but the concentration of linoleic C18:2 is higher than the concentration of linolenic C18:3 ; our results showed that the content of linoleic ranges from 9.1-14.1 compared to 0.53-0.93 for lin-    (2) study is similar to that found by previous reporters 53, 54 and higher than that reported by another investigator 15 .
It is also interesting to compare the concentration of monounsaturated fatty acid oleic acid/cis isomer C18:1 with polyunsaturated fatty acids of C18 linoleic C18:2 , and linolenic C18:3 . Results of the current study revealed that the content of cis oleic acid monounsaturated fatty acid is the highest range: 60.4-69.3 followed by linoleic acid C18:2 range: 9.1-14.1 and linolenic C18:3 range: 0.53-0.93 . The percentage of palmitoleic acid C16:1 cis was found to range from 0.35 -1.12 which is comparable to linolenic acid C18:3 .
Olive oil contains more oleic acid and less linoleic and linoleic acids than other vegetable oils, that is, more mono-unsaturated MUFA than polyunsaturated fatty acids PUFA . This makes olive oil more resistant to oxidation. The greater the number of double bonds in the fatty acids, the more unstable the oil becomes and easily broken down by heat, light, and other factors. It is generally accepted that cooler areas will yield oil with higher oleic acid than warmer climates, which means that a cool olive oil region may have more MUFA content than oil in warmer regions 55 .
Fatty acid composition is important for the commercial properties of oil and can influence the stability of oils due to the contribution of PUFAs to oil rancidity. In addition, several studies have shown that a diet rich in MUFAs may result in a wide range of health benefits such as an improvement in cholesterol levels, and, in turn, prevention of cardiovascular disorders 15 . In particular, high levels of MUFAs mainly oleic acid , which have health benefits, are important for human nutrition and are among the major components of the Mediterranean diet, playing an important role in the nutritional value of table olives 16,44,49 .
The major fatty acids in table olives are oleic, palmitic, stearic, linoleic and palmitoleic acids 12,56 . Because table olives are mainly composed of MUFAs, their consumption can prevent and reduce the risk of cardiovascular diseases, regulate cholesterol levels, stimulate transcription of LDLcholesterol receptor mRNA, and reduce breast cancer risks 40 .
composition in olive oil extracted from different olive cultivars grown in the Calabrian area found the content of C20:0 ranged from 0.02 -0.4 . Concerning C22:0 content, results Table 9 showed that there was no significant difference in content between the From these results, it is evident that the MUFA content     (14), Sinieria (15).
oleic and palmitoleic is higher than PUFA linoleic and linolenic and SAFA. Monounsaturated oleic acid is distinctly predominant, followed by saturated palmitic acid and polyunsaturated linoleic acid.
Interest has increased in olive varieties with higher oil content OC , improved fatty acid composition, mainly high monounsaturated fatty acids MUFAs and a high content of phenolic compounds due to its stability and health benefits 12,56 . While OC is associated with oil quantity and olive growing profitability, proportions of the different fatty acids and phenolic compounds are associated with oil quality. For example, a high MUFA percentage, mainly oleic acid, is a primitive factor in determining the nutritional value of the oil as it reduces the risk of atherosclerosis and protects against different cancers 49 . In addition, fatty acid composition influences the stability of the oil through the contribution of polyunsaturated fatty acids PUFAs to oil rancidity 16,44 . Table 13 shows mean values, standard deviations SD , minimum values, and maximum values of variables determining oil quality polyphenols, acidity and peroxide value and different fatty acids of old olive trees in various loca-tions in Palestine pooled data in 2008 and 2009 . While Table 14 shows the same parameters for the year 2010 as well as pooled data for the three years of the study.

Pooled results from the different years
As obvious from this table, the average polyphenolic content of the pooled data in 2008, 2009, and 2010 is 386, 458.9, and 327.3 mg/kg, respectively, with a pooled average of 366.0 mg/kg for the three years. There is also a high standard deviation 166.7 indicating a wide range of polyphenolic content among the samples in various locations in the West Bank. The same was obtained for the other two parameters determining oil quality percent acidity and peroxide value see Tables 13 and 14 .
The pooled mean of palmitic acid percentage C16:0 was found to be 13.30, 13.41, and 13.30 for the years 2008, 2009, and 2010, respectively with a pooled value of 13.31 for the three years indicating comparable content. The same was conducted for the other fatty acids as shown in Tables 13 and 14.

Ratio indicators for olive oil quality
It is interesting to find the sum ratio of unsaturated fatty acids mono and poly to the sum of saturated fatty acids USFA/SFA which was found as 4.54, 4.47, 4.33 for the pooled data of 2008, 2009, and 2010, respectively with a  pooled value of 4.43 for the three years, indicating comparable ratio. Another ratio was calculated between the sum of monounsaturated fatty acids to the sum of polyunsaturated fatty acids MUFA/PUFA which was determined as 5.97, 6.50, and 5.19, for the pooled data of 2008, 2009, and 2010, respectively with a pooled value of 5.63 for the three years. The ratio was also calculated between the oleic to linoleic fatty acids C18:1/C18:2 which was found to make up 6.14, 6.66, and 5.35, of the pooled data of 2008, 2009, and 2010, respectively with a pooled value of 5.79 for the three years. These ratios serve as indicators of the olive oil quality where the quality becomes good as they increase. The ratios also strongly influence olive oil oxidative stability and health benefits 50,57 . On the other hand, lower ratios between PUFA and SFA PUFA/SFA are linked to higher stability of olive oils. This ratio PUFA/SFA was calculated for the pooled data of 2008, 2009 and 2010 and was found to represent: 0.65, 0.59, and 0.70, respectively with a pooled value of 0.66 for the three years.
The high ratio of MUFA/PUFA and C18:1/C18:2 and the low PUFA/SFA ratio is linked to high oxidative stability and low rancidity of olive oil 43 ; in combination with other minor compounds, this affects the organoleptic and health properties of olive oil 10, 58, 59 .

Pearson correlations
Initially Pearson correlations were calculated to test the relation among quality indicators determining oil quality polyphenols, acidity and peroxide value and different fatty acids in each study year separately and when data were pooled. The NOMISS option was used in order to obtain results consistent with subsequent multiple regression studies.

Conclusion
This work outlines some olive oil quality parameters fatty acid profile, acidity levels, peroxide value, total phenolic content of old olive trees in Palestine. The fatty acid trends showed characteristics typical of virgin olive oil. Acidity levels and peroxide values were also typical of virgin olive oil. The olive oil samples were rich in polyphenolic compounds reflected by total phenolic content. Oleic, palmitic, stearic, linoleic, and palmitoleic acids are the major fatty acids in the olive oil samples with more monounsaturated MUFA than polyunsaturated fatty acids PUFA . Some correlations between total phenolic content, peroxide value or percentage of acidity and fatty acids were observed. Fatty acid composition varies according to the evaluated geographic region in West Bank although wide ranges of variance were obtained in the collection year.

Author Contributions
The research was designed and conducted by T. Hijawi. Additionally, T. Hijawi analysed data and results and wrote the manuscript.