KARACHI, Nov 19: Two of the largest-selling locally-made edible oil brands don’t conform at all to the universally-recognized standards. Excessive use of these brands, therefore, could spell trouble.
Carefully conducted chemical analyses have revealed that even the products’ iodine values — considered to be their fingerprints — don’t fall within the range recognized as standard by the World Health Organization (WHO) and Food and Agriculture Organization (FAO) of the United Nations.
Under the study — conducted by Hina Sheikh, an MPhil student of Karachi University’s food sciences department — samples of one popular brand each of corn oil and soybean oil were tested and their values for iodine, peroxide and free fatty acids were determined. None of the values obtained fell within the range held as standard both by the WHO and FAO.
The WHO/FAO joint standards require that iodine value of corn oil be between 103 and 135 units. The iodine value of soybean oil, on the other hand, should be 130.
Upon testing the iodine values of the corn oil and soybean oil samples were found to be less than 45 units. There was, therefore, a big difference between the samples’ iodine values and those prescribed by the WHO and FAO.
The peroxide values for both corn oil and soybean oil should be less than 10. The tests showed that the samples’ peroxide values were more than 12.
Similarly, according to the WHO/FAO Food Standards, the free fatty acids’ values for both the oils should be less than 0.6. The samples’ values were found to be about 2.0, which represents a big variance.
Shahina Naz, Karachi University’s faculty member who supervised the analyses, told Dawn that low iodine values in the samples showed the oils could solidify at room temperatures. “In other words, these oils behave like ghee, which remains solid at room temperature,” she said.
People who prefer edible oils over ghee do so because these tend to control cholesterol and prevent formation of clotting in blood. “But oils having low iodine values don’t have much ability to prevent clotting and lowering cholesterol levels. These oils may actually be harmful, like ghee.”
She was of the view that low iodine number indicated the presence of certain additives or foreign matter in the oils tested. “The iodine numbers are considered to be chemical fingerprints of sorts,” she said. “These numbers actually indicate the purity of oils etc.
“The fact that the samples didn’t have the required iodine numbers show that the oils aren’t pure, even though all the adverts claim they are 100 per cent pure.”
Rahmanullah Siddiqui, another faculty member, said palm oil — being cheaper than corn and soybean oils, could have been added to the products. “Some tests should be conducted to confirm this theory. But I still think that palm oil may have been added.”
The samples’ high peroxide values indicate that these had undergone oxidation, said Mrs Naz. “High peroxide values show there was excessive oxidation.
“Excessive oxidation can result in the formation of certain undesirables in the products. Some of the compounds, formed after oxidation, are very harmful.”
Mr Siddiqui told Dawn that high values for free fatty acids don’t spell too much trouble in case the products are used properly. “However, if the oils are used and heated several times before discarding, then acrolines could be formed in the oils.
“Acrolines are very dangerous as they are carcinogenic, that is they can cause cancers if consumed in excessive amounts.”
