Physicochemical properties and Trace metal level of oils sold in Ethiopia and their effect on the serum of rats
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Date
2015-06
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Addis Ababa University
Abstract
Objective: Considering the fact that elevated serum concentration of cholesterol is a major risk
factor for atherosclerotic disease, the effect of consumption palm oil, soya bean oil, Sheno lega
and Niger seed (Nuge) oil-supplemented diet on serum lipid profile of Wistar albino rats was
investigated. These oils were analyzed spectrometrically for their metal (Cu, Fe, Pb, Ni, and Zn)
levels by Graphite Furnaces Atomic Absorption Spectrometer. The four samples of vegetable oils
were also examined for peroxide value, acid value, iodine value and % free fatty acid (%FFA).
Methods: Growing male Wistar albino rats (Rattus novergicus) weighing (165-220g) were used
for this study. The rats were housed individually in cages in groups of 4, and maintained at room
temperature (21oC + 2oC) with 12 hrs light and dark cycles. Each group had 6 rats and fed with
10% palm oil, 10% Soya bean oil, 10% Sheno lega and 10% Niger seed (Nuge) oil -
supplemented diets for 12 weeks. The blood samples were drawn by cardiac puncture after 4, 8
and 12 weeks. The serum levels of Total cholesterol (TC), Triglycerides (TG), Low-density
lipoprotein (LDL), and High-density lipoprotein (HDL) were determined at 4-, 8-, and 12-week
intervals. The trace metals levels of Copper, iron, zinc, Nickel and lead were determined by
AOAC 1995 official method 990.05 by using GF AAS, after extracted from low quantities of oil
(0.3290-0.3590 g ) with a 65% nitric acid solution and Hydrogen per oxide30% using Microwave
assisted digestion and quantization after preparing series of working standard solutions by
diluting metal stock solution with deionized water to set calibration curve. Physicochemical
analysis peroxide value (PV), iodine value (IV), were determined following the method of the
AOAC official method 965.33 (2000) and AOAC official method(1995) respectively . The acid
value (AV) was determined titrimetrically using the procedure of AOAC official method 940.20
(1995). Results: In sheno lega group, 4 weeks of sheno lega supplemented fed significantly (p<0.05)
increased serum total cholesterol than did Niger seed, palm oil or soya bean oil supplemented
group . After 8 weeks of fed TC was highest in sheno lega supplemented group. After 12 weeks
of fed TC decrease by all groups but no statistical difference was observed by palm oil and Niger
seed group. High Density Lipoprotein Cholesterol (HDL-c),In sheno lega group, 4 weeks of
Sheno lega supplemented fed significantly(p<0.05) increased HDL-c than Niger seed oil, Palm
oil or soya bean oil supplemented group. Niger seed oil supplemented group showed significant
increase (p<0.05) after 8 weeks of fed. After 12 weeks neither group showed difference. Low
Density Lipoprotein Cholesterol (LDL-c), in palm oil, 4 weeks of Palm oil supplemented fed
significantly (p<0.05)increased serum LDL-c than Soya bean oil, Sheno lega or Niger seed oil.
After 8 weeks of fed, Niger seed oil supplemented group showed significant increased (p<0.05).
After 12 weeks of fed Niger seed oil supplemented group showed significance higher value.
Triglyceride (TG), in sheno lega group, 4 weeks of sheno lega supplemented fed showed
increased serum TG. After 8 weeks of fed TG was significantly (p<0.05) increased by sheno lega
supplemented group. After 12 weeks of fed all groups decreased TG but Sheno lega showed
higher level. Trace metal level Cu (0.1715 μg/g) was found the highest metal concentrations in
Niger seed oil, Sheno lega for Ni (1.7187 μg/g), Niger seed oil for Fe (4.082 μg/g), Soya bean oil
contain lower amounts for Fe (2.453 μg/g), and Niger seed (Nuge) oil for Ni (0.8584 μg/g)
compared to the other vegetable oil, Pb and Zn were not detected. Niger seed (nuge) oil with the
highest acid value 10.84, Sheno lega, Palm oil and soya bean oil have 1.96, 1.54 and 1.47 mg
KOH/g acid value respectively. Per oxide value was 6.40, 4.10, 3.99 and 3.10 meq.peroxide/kg in
Niger seed oil, Soya bean oil, Sheno lega and Palm oil respectively. Iodine value 128.30, 112.56,
54.56 and 3.77 in Soyabean oil, Niger seed oil, Palm oil and Sheno lega respectively. Percent
Free fatty acid (%FFA) 5.45, 0.99, 0.77, and 0.74 in Niger seed oil, Shenolega, palm oil,
soyabean oil respectively. Conclusions: In short fed sheno lega acutely raises serum total cholesterol. After long fed fed palm oil and Niger seed oil rise serum total cholesterol but no difference showed between palm oil and Niger seed oil. In short fed sheno lega acutely increased HDL-c, Niger seed oil showed chronic effect. In short fed Palm oil acutely raises LDL-c. Chronic effect on LDL-c is the same by all oil types. Sheno lega affects triglycerides level in both acute and chronic use. Fe in all Oil groups were above the maximum values recommended for FAO/ WHO(2011). Cu level in Niger seed oil was above the maximum values recommended for FAO/WHO (2011), Nickel level in sheno lega and palm oil was above the margin approved requirement. The peroxide value and acid value in was highest for Niger seed oil . Acid value was above permissible value in all groups. Sheno lega existed with more saturated fatty acid with lowest iodine value.
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Food and Nutritionl Science