الفهرس 
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Abstract
Egyptians consume high amounts of oils and local oil production is not sufficient to cope with our needs. This work was conducted to improve sunflower oil, palmolein oil frying and nutritional properties by blending with olive oil to get high stable clear liquid frying oil. Results indicated that the physical, chemical characteristics and the fatty acid composition of fresh sunflower oil (SO), palmolein oil (SoO) and olive oil (OO) were as reported in the Egyptian standard for oils. Blending was carried out using SO or SoO at percentages ranged from 70 to 90% and OO at percentages ranged from 30 to 10 % . The obtained results indicated that the clear liquids blends with higher content of mono-unsaturated fatty acids were:- Blends: (B3) [SO (70%) + OO (30%)] and B6 [SoO (70%) + OO (30%)].
SO, B1, B2, B3 and SoO, B4, B5, B6 frying oils were used in intermittent frying of potato slices at 180°C for 30 hours with replenishment. The effect of blending on physical and chemical properties during frying was studied and the results indicated as followed. The results can be summarized as follows 1.Blending caused an increase in oxidative stability of sunflower oil from 7.5 days to 11.7 days and palmolein oil from 12.6 to 31.2 days.
2.Smoke point decreased from 237, 254,257,259 and 241, 256, 258, 265°C before frying to 192, 206, 214, 220 and 218, 221, 225, 230°C after 30 hours frying for sunflower oil, B1, B2, B3 and palmolein , B4, B5, B6, respectively.
3.The colour of the investigated oils increased from 1.3, 1.4, 1.8, 2.1 red at 35 yellow to 22.4, 15.9, 14.2, 12.9 red at 35 yellow after 30 hours frying for sunflower oil, B1, B2, B3 and from 2.5, 2.7, 2.8, 2.9 to 17.9, 15.4, 14.6, 13.7 red at 35 yellow after 30 hours frying for palm olein , B4, B5, B6, respectively.
4.Viscosity increased from 45, 45, 40, 40 CTP to 100, 90, 85, 80 CTP after 30 hours for sunflower oil, B1, B2, B3 and from 70, 70, 65, 60 to 1520, 1500, 1490, 1420 CTP for palm olein , B4, B5, B6, respectively.
5.Frying caused significant increase in U.V. absorption from 1.16, 0.83, 0.71, 0.61 to 1.96, 1.84, 1.75, 1.579 and from 0.822, 0.316, 0.34, 0.742 to 2.712, 1.574, 1.715, 1.794 at 234 nm and from 0.189, 0.0103, 0.077, 0.042 to 1.123, 1.017, 0.937, 0.813and from 0.174, 0.101, 0.065, 0.039 to 1.025, 0.967, 0.905, 0.801 at 268 nm after 30 hours frying for sunflower oil, B1, B2, B3 and palm olein, B4, B5, B6 respectively.
6.Refractive index at 25°C increased from 1.4704, 1.4702, 1.4701, 1.4700 and 1.4649, 1.4648, 1.4647, 1.4647 to 1.4731,1.4728, 1.4727, 1.4725 and 1.4665, 1.4664, 1.4663, 1.4661 after 30 hours frying for sunflower oil, B1, B2, B3 and palmolein , B4, B5, B6 respectively.
7.The acid value increased progressively during frying but the increase was more pronounced in sunflower oil and palmolein oil after frying for 30 hours when compared to B1, B2, B3 and B4, B5, B6. Peroxide value increased during frying in all two investigated oils and oil blends but more in SO, SoO than blends.
8.The TBA values of the frying oils increased gradually with the increase of frying time in all the investigated oils but less in B3 and B6 than others, and these values fluctuated at the last stage of frying.
9.The polymer materials formed in sunflower oil, B1, B2, B3 and palm olein, B4, B5, B6 increased from 0.025, 0.023 , 0.021, 0.02 and 0.018, 0.018, 0.015, 0.014 % at zero time to 2.99, 2.95, 2.89, 2.83 and 2.95, 2.9, 2.85, 2.79 % after 30 hours frying, respectively.
10.Oxidized fatty acids increased with the increase of time frying and sunflower oil and palmolein oil became rejected ”approx. 1% oxidized fatty acids” after 8 hours of frying compared toblends which ranged from 16 to 20 hours of frying for B1, B2, B3 and B4, B5, B6.
11.During frying of sunflower oil, B1, B2, B3 and palmolein, B4, B5, B6 the fatty acid composition changed as the linoleic acid content decreased and the oleic acid increased but pronounced in SO and SoO.
12.The percentage of oleic acid found in 2- position of triglyceride composition increased in blending oils than sunflower oil or palmolein oil. The high percentage found in B3 and B6.
13.The increase in the added amount of olive oil to sunflower oil was associated with marked increase in the major volatile compounds in olive oil, 2- hexenal, 2,4 – heptadienal, octanal and 1-pentene-3-ol were the predominate compounds in olive oil and the addition of olive oil to palmolein oil showed the same behavior. After frying , the volatile compounds increased in SO or SoO than in their mixtures.
14.The organoleptic evaluation (i.e., color, taste, odor). showed that potatoes fried in blend (3) or B (6) were rejected organoleptically after 20 hrs wherease other oils ( SO, SoO, B1, B2, B4, B5) after 10 or 15 houres of heating
In the second part, biochemical evaluation or nutritional experiments were conducted to indicate the safety of sunflower oil, palmolein oil and their blends with olive oil (B3, B6) for deep fat frying. These biochemical parameters were measured in the serum of rats fed on diets containing non- fried oils (SO, SoO) and its blends (B3, B6). The biochemical parameters include:-Rat liver functions: alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP); some serum contents such as total lipids, total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and Low-density lipoprotein cholesterol (LDL-C); kidney functions urea , uric acid and creatinine ; malondialdhyde in serum and glutathione peroxidase in blood .
Histopathological examinations were conducted on liver, kidney and heart tissue of rats administrated the above mentioned oils.
Biochemical evaluation of non fried and fried sunflower oil, palm oils and blends B3 , B6 were summarized as :-
15.Weight of rats (wt gain) fed on non-fried oil and fried oils (15 hrs frying) had no significant change whereas their weight gain decrease for oils (30 hours frying).
16.The administration of fried oils to rats for 8 weeks induced significant rises in ALT, AST and AP. Also, these feeding experiments possessed increased in the levels of total lipids, total cholesterol, urea, uric acid, creatinine and significant effect on LDL, HDL, triglyceride, malondialdehyde and glutathione peroxidase in blood. The administration of fried – treated oils (15 hrs of frying) to rats indicated that the activities of kidney, liver, heart and peroxidase enzymes were parallel with the data of administration of non – fried oils to rats. Also, the levels of serum continents were significantly increased due to frying in a similar manner to that of fresh oil but the rats fed oils of 30 hrs frying show the maximum values of these serum functions.
17.Palm oil and B6 exceptionally behaved in a different manner to those of sunflower oil and B3. Palm oil and B6 raised serum total cholesterol and LDL-C, while lowered serum HDL-C. These results were due to the presence of high levels of saturated fatty acids in palm oil.
18.Microscopical examinations of liver, kidney and heart tissues of rats administered diets containing non-fried sunflower oil (SO), non-fried palmolein oil (SoO) and the mixtures of them at ratio 70: 30 with olive oil (v/v) (SOO, SoOO) indicate apparent normal hepatocytes without any microscopic sign of toxicity and after frying for 15, 30 hrs. The histopathological examination of liver kidney and heart of rats administered the fried- mixed oils indicated changes in the tissues parallel with the data of biochemical tests for liver, kidney and heart function tests of non- fried and fried oils.
Conclusion
In conclusion, the included data revealed that, the addition of olive oil(30%) to sunflower or palmolein oil improved nutrition quality and frying stability of either sunflower or palmolein oil during frying up to 20 hours at 180 ± 5°C with respect to oxidized fatty acids percentages, peroxide value, acid value and polymeric compounds.
The results also showed that the oxidized fatty acids and polymeric compounds were formed in all treatments as a result of frying however, more oxidized fatty acids and polymeric compounds were formed in sunflower oil and palmolein oil than their blends (B3, B6).
The results further showed that blends containing 30% olive oil with sunflower or palmolein oil were more resistant to the formation of oxidized fatty acid and polymeric compounds. So, they are more stable against thermal oxidation during frying process.
Nutritionally, it is remarkable that rats fed on either B3 or B6 had lower toxic effects on rats serum functions (Kidney, liver and Heart) and that also showed from the histopathology results.