Deep-Frying with Thermoxidized Groundnut Oil Is a Potential Source of Free Radicals with Health Hazards
Groundnut oil is one of the most commonly used vegetable oils in the household and industry in Nigeria for deep frying purposes. This research work was aimed at evaluating the effects of thermoxidized and fresh groundnut oils on lipid peroxidation, in vitro radical scavenging and in vivo antioxidant activities. The study comprised thirty-five (35) wistar albino rats divided into seven (7) groups of five (5) rats each. The different groups excluding group one (1) were fed with animal feeds containing various doses of the oils in their feed for six (6) weeks. Different methods of analyses, ranging from colorimetric, titrimetric, spectrophotometric, and hyphenated mass-spectroscopy were employed to obtain the results. The study showed that the peroxide and acid values (responsible for the off-flavour due to rancidity), DPPH and FRAP (which give a measure of the pro-oxidant capacity) were significantly (p<0.05) increased in the thermoxidized oils when compared to the fresh edible oils. Also, SOD, CAT (responsible for the antioxidant activity) and MDA values (a measure of peroxidation of a sample) increased significantly (P<0.05) in the thermoxidized groups. The GC-MS analyses also revealed that the thermoxidized oil samples produced compounds which are toxic or carcinogenic, like Butane, 1-[(2-methyl-2-propenyl)oxy]-, 4-n-Hexylthiane, (R)-,1,6-Octadiene, 5,7-dimethyl-, (R)- and Cyclododecanol, 1-aminomethyl and (R)-(-)-14-Methyl-8-hexadecyn-1-ol. The above findings suggest that there are potential health hazards associated with the consumption of oxidized products resulting from these oils used repeatedly in frying processes. In light of these findings, it is recommended that consumption of groundnut oils subjected to heating for long periods of time should be discouraged in Nigeria and other Low and Medium Income Countries (LMIC) where such practices are common.
Keywords: Edible oils, Deep-frying, Antioxidants, Radical scavenging, Lipid peroxidation.
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