الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
This study was carried out to investigate the effect of different processing steps of extraction virgin olive oil as well as amount of water added to decanter during extraction with centrifugation system three phase (400, 600 and 800 liter/tone) to give the highest oil yield of good quality. Furthermore, the effect of washing oil by separator system (0, 50 and 100 water) was also studied. The obtained results could be summarized as follows:
1-The chemical composition of Cortina olive fruit was studied and results indicated that moisture content of olive fruit was 57.7 %, while crude oil (on dry basis) was 52.46 %.
2-The refractive index of both paste oil after crushing and malaxation were 1.4675 and 1,4678 at 25 °C respectively The refractive index for olive oil from decanter was 1.4680 at 25 °C. No change in refractive index with using adding different amounts of water. The refractive index for each of virgin olive oil washed with 0%, 50%, and 100% water was 1.4678, 1.4678, 1.4680, respectively. It means that there was no significant difference between 0%, 50% and 100%. Also, the refractive index took the same trend in oil pomace .
75 Summary
3-The color for virgin olive oil from olive paste oil after crushing and malaxation was 3.1, 4.0 red and 2.8, 4.3 blue at 35 yellow, respectively. The oil color of decanter, by addition of 400, 600, 800 liter of water was 4.4, 4.3, 4 red and 4.1, 3.9, 3.6 blue at 35 yellow, respectively. Increase of washing with 0, 50 and 100 % water decreased the color of oil with 4.3, 3.7, 2.4 red and 3, 3.2, 2.2 blue, respectively.
4-Values of K232 and K270 for virgin olive oil after malaxation were 0.298 and 0.0374, respectively higher than there after crushing as they reached 0.287and 0.035, respectively. Addition of different amounts of water (400, 600, 800 L/tone olive paste) from decanter increased the absorbency at K232 and K270. The values of absorbency for K232 after addition of water to decanter were 0.31, 0.38, 0.52, respectively, while those of K270 were 0.038, 0.04, 0.049, respectively. Washing oil with 0, 50%, 100 % water increased values of K232 to 0.32, 0.36; 0.39 and K270 to 0.038, 0.041, 0.036, respectively.
5-The acidity for olive oil after crushing and malaxation was 0.21 % and 0.52 %, respectively, however no change in total acidity was observed during washing. On the other hand, addition of water to pomace oil raised the acidity.
6-The peroxidase activity in malaxation step was 9.8 meq/Kg oil. Also, the peroxide value increased by addition of water to decanter. After addition of water by 400, 600 and 800 L/ton to olive paste, the peroxide value was 9.8, 10.36 and 11.22 meq/Kg oil, respectively, and the same values of separator No.1
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and 2. showed no effect on the peroxide value in pomace olive oil.
7- The iodine values of virgin olive oil after processing steps were 80.53, 80.76, 80.84, 80.84, 80.82 (crushing, malaxation, decanter, separator 1, and separator 2) respectively. No change in iodine value (around 80.8 meg/kg olive oil) when using different amounts of water (400, 600, 800 liter water/ 1000 Kg olive paste) to oil from each of the decanter, separator No. 1 and separator No.2. There was no effect on iodine value of virgin olive oil washed with 0, 50, and 100% water, As it reached 80.84, 80.83 and 80.82 meg/kg olive oil. Also, there was no effect on the iodine value of olive oil pomace during extraction with addition of water to the decanter which were 78.67, 78.62, and 78.66 meg/kg olive oil.
8-The percentage of the unsaponifiable matter of olive oil extracted from different processing steps (after crushing, malaxation, decanter, separator No.1 and separator No.2) were 1.29, 1.30, 1.41, 1.39, 1.38, respectively. There was slight decrease in unsaponifiable matter by addition different amounts of water.
9-The tocopherol in virgin olive oil after crushing and malaxation obtained nearly the same value. The tocopherol content in olive oil from decanter after addition different amounts of water was 233, 235, 230 mg/kg, respectively. Tocopherol content of oil in separator No. 1 and separator No.2 was nearly the same. After
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11 In this study, there is a decrease in oxidative stability of paste
oil after crushing and malaxation as it was 53.2 , 47.8 hrs at 100 °C. Addition of water diluted the olive paste before it was centrifuged decanter and lowered the level of antioxidants. Washing virgin olive oil in separator decreased the oxidative stability from 46.28 to 32.9 hrs. On the other hand, addition of
water decreased oxidative stability for 10.6, 9.2 , 6.25 hrs at 100°C, respectively.
washing with water no change in virgin oil was observed for tocopherol content.