Characterization of Oils Bleached with Clays Using Trace Metals, Peroxide, Acid, and Iodine Values

Abstract

Edible oil bleaching is known to change the composition of oils by removing contaminants and some food components. The type of bleaching media, the temperature at which the bleaching is done, and other parameters all influence the characteristics of bleached oil. To determine the characteristics of edible oils bleached using smectite and kaolinite-rich clays, we compare peroxide, free fatty acid, acid and iodine values, copper and iron content of bleached and crude oils. Oil companies spend a lot of money on bleaching earths, although every country has natural clays that can be used to bleach oils. Every month, more than US$ 700,000 is spent in Uganda alone, although many clay deposits remain untapped. The trace metal composition, peroxide values, acid values, iodine values, and free fatty acid content of bleached and unbleached cotton-seed and sunflower seed oils were all described in this study. The bleached oils were shown to be safe for human consumption. Clays are collectively called alumino-silicates as they contain aluminium oxide and silicon dioxide as universal minerals.   Clays are either kaolinites or smectites, but montmorillonites or bentonites are employed to bleach edible oils. The bleached oils had the greatest reduction in iron content of all the bleached oils. Copper was the element with the smallest change. The content of copper in cotton oils decreased from 0.5 ppm to 0.15 ppm using Kajansi clay leached in 20% acid yet when Chelel clay leached under similar conditions was used decrease was from 0.5 to 0.1 ppm. Iron concentration in sunflower oils bleached with Kajansi clay leached in 20% acid fell from 1.6 to 0.2 ppm, but it decreased to 0.1 ppm when bleached with Chelel clay under comparable conditions. The acidity of sunflower oils is primarily attributable to oleic acid, since the average value for acids is in the range of oleic acid, while cotton-seed oil corresponded to linoleic acid. The levels of free fatty acid were found to lie in range from 3.8 - 3.2 for all clays used showing no significant rise. The peroxide values of bleached oils lay between 1.2 and 0.8.