الفهرس 
Introduction
Physical and chemical properties of olive oilOnly 14 pages are availabe for public view
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Abstract
Virgin olive oil is the oil obtained from the fruits of the olive tree (Olea europea) by mechanical or other physical means under conditions, particularly thermal, which do not lead to alteration of the oil. Virgin olive oil is an oil which is suitable for consumption in the natural state.
The increasing levels of olive oil consumed around the world were caused by its beneficial health properties, which have been known for centuries, particularly in the Mediterranean region.
Virgin olive oil is recognized as one of the best vegetable oils given its nutritional benefits in the human diet. Virgin olive oil is also more stable oil than other edible oils because of its high content of phenolic compounds, -tocopherol, carotenoids and mono-unsaturated fatty acids. One of the most important characteristics of olive oils is the presence of a high content of oleic acid. Which accounts for 60-80% of the total fatty acids and for approximately 90% of the mono-unsaturated fatty acids.
The present investigation was carried out on fruits of four olive cultivars namely; Chemlali, Kronaki, Frantoio and Pecual obtained from El-Dakhala Oasis, New Valley Governorate.
The physical and chemical properties of the extracted oils of the four studied olive cultivars, as well as fatty acids and unsaponifiable matter composition were determined by GLC method. The total polyphenols were extracted and quantitatively determined by HPLC method. On the other hand, measurement of oxidative stability and antioxidant activity of virgin olive oil were performed by rancimate, in comparison with sunflower oil.
As well as the effect of using different levels of studied olive oils on blood serum lipids (triglycerides, total cholesterol, HDL-cholesterol, LDL-cholesterol and VLDL-cholesterol) of rats was studied.
The obtained results could be summarized in the following points:
1. Refractive index of studied samples were 1.467, 1.467, 1.471 and 1.468 for Chemlali, Kronaki, Frantoio and Pecual, respectively.
2. Chemlali fruits had the highest oil content (47.20%) on dry weight basis, while Pecual fruits recorded the lowest oil content with percentage of 35.40%.
3. Chemlali cultivar recorded low acid value (0.738%). Meanwhile, Kronaki, Frantoio and Pecual samples recorded the highest values (0.845; 0.828 and 0.860%, respectively).
4. The mean values of iodine number ranged from 82.50 for Chemlali oil to 86.50 for Kronaki oil. There were significant differences in iodine values between all studied olive cultivars.
5. The peroxide values of oils extracted from Chemlali, Kronaki, Frantoio and Pecual cultivars were 10.98, 8.80, 8.77 and 9.68 meq/kg of oil, respectively.
6. Conjugated diene had the values of 0.288, 0.183, 0.181 and 0.227 for Chemlali, Kronaki, Frantoio and Pecual olive oils, respectively. On the other hand, the values of triene recorded 0.157, 0.103, 0.095 and 0.145 for oils extracted from Chemlali, Kronaki, Frantoio and Pecual olive cultivars, respectively.
7. Kronaki oil recorded the highest percentage of unsaponifiable matter (1.81%). Meanwhile, the lowest value was recorded for Pecual cultivar as it was 1.36%, followed by Frantoio and Chemlali oils (1.49% and 1.62%, respectively).
8. Kronaki cultivar oil recorded the highest oxidative stability (26.20 hr), while the lowest value (19.40 hr) was recorded by Pecual cultivar oil. On the other hand, the oxidative stability of both Chemlali and Frantoio oils recorded 23.80 hr and 21.60 hr, respectively.
9. With regard to the fatty acid composition, oleic acid was the predominant unsaturated fatty acid, followed by linoleic acid. Besides, palmitic acid was the major saturated fatty acid in all studied olive cultivars.
10. Oleic/Linoleic acid (O/L) ratio of virgin olive oil varied from 2.53 for Chemlali to 5.61 for Kronaki.
11. Pecual and Kronkai oils, had higher content of total unsaturated fatty acids (81.029% and 81.020%) than Frantoio and Chemlali which recorded (76.838% and 73.847%), respectively.
12. There were considerable differences in total polyphenols content between virgin olive oils extracted from all studied olive cultivars. Moreover, the total polyphenols of Kronaki virgin olive oil recorded 362 ppm, which is higher than the corresponding total polyphenols of Chemlali, Frantoio and Pecual virgin olive oils, which recorded 320, 270 and 180 ppm, respectively.
13. HPLC analysis for the total polyphenols extracted from olive oil cultivars indicated that considerable variation was found in the phenolic compounds of the different olive cultivar oils.
14. p-coumaric acid was the major polyphenol compound in all studied samples. It represented 23.108, 22.140, 23.231 and 21.519% of total polyphenols in Chemlali, Kronaki, Frantoio and Pecual cultivars, respectively.
15. Caffien was found as the second major phenolic compound in all olive cultivar oils, comprising 21.219, 20.186, 20.735 and 18.106% of the total polyphenols in Chemlali, Kronaki, Frantoio and Pecual cultivar oils, respectively.
16. The data showed that the compounds of phenolic acids such as p-benozic, caffeic, ferulic and cinnamic acids are the third group of phenols observed in virgin olive oils. Meanwhile, gallic acid, catechol, syringic acid, coumarin and chrisin recorded the lowest levels in all studied olive cultivar oils.
17. The addition of total polyphenols extracted from virgin olive oils of studied olive cultivars at 400 ppm level led to improve sunflower oil stability.
Data revealed that sunflower oil recorded the highest stability by using polyphenols extracted from Kronali olive oil (15.56 hr. Induction period and 1.87 antioxidant activity).
18. Unsaponifiable matters of virgin olive cultivar oils were fractionated by GLC technique. It consisted mainly of hydrocarbon and sterols.
Sterol fraction represented about 29.60, 29.84, 29.45 and 29.05% of the total unsaponifiable matters of Chemlali, Kronaki, Frantoio and Pecual cultivar oils, respectively. Whereas, hydrocarbon fraction represented about 70.40, 70.16, 70.55 and 70.95% of the total unsaponifiable matters of Chemlali, Kronaki, Frantoio and Pecual olive cultivar oils, respectively.
19. -sitosterol was the major sterol component in all studied samples, while squalene was the predominant component of hydrocarbons in all studied samples.
20. Rats fed on Rich Cholesterol Diet (RCD) lead to raised serum cholesterol level. The higher increasing was in LDL-cholesterol (60.22%), then triglycerides and VLDL-cholesterol (52.4%). Total cholesterol raised within (32.29%), however HDL-cholesterol decline within (26.90%).
21. The highest decrease in rat serum triglycerides was in groups feeding on virgin olive oils extracted from Kronaki cultivar at 4 ml of olive oil after 50 days of treatment (142.80 mg/dL), followed by Chemlali, Frantoio and Pecual olive oil cultivars in the descending order.
22. The highest decrease in rat serum total cholesterol was in 4 ml of Kronaki virgin oil after 50 days, whereas the lowest decrease was in groups feeding on Pecual virgin olive oil.
23. The highest levels of HDL-cholesterol were showed for rats fed on 4 ml of virgin olive oil of Kronaki, Chemlali, Pecual and Frantoio cultivars, respectively. On the other hand, adverse trend of rat serum HDL-cholesterol level shown in LDL-cholesterol level, where as data showed that the highest decrease in rat serum LDL-cholesterol was found in rats fed on 4 ml of Kronaki virgin olive oil followed by Chemlali, Pecual and Frantoio cultivars, respectively.
24. The trend of serum VLDL-cholesterol level in rat during experimental period was same with serum triglyceride trend due to that virtually all of the plasma triglyceride is carried on VLDL.
from these results, it could be concluded that the amount of phenolic compounds in virgin olive oils is an important factor when evaluating the quality of virgin olive oil because polyphenols are recognized as antioxidant compounds and their presence in olive oils has been related to their general quality, improving stability, nutritional value and sensorial properties.
In addition, it is safety to use the natural antioxidants rather than the artificial ones BHT which are definitely harm to the human health.
Virgin olive oils are consider as a good treatment for decreasing serum total cholesterol, LDL-cholesterol, VLDL-cholesterol and triglycerides, as well as increasing HDL-cholesterol.