Using trace metals, peroxide, acid and iodine values to characterize oils bleached using clays from Central and Eastern Uganda

Abstract

The decrease in content of iron in the bleached oils was highest for all oils bleached. The content of copper showed the smallest change. The decrease in copper content for palm oils decreased from 0.2ppm to 0.1ppm when bleached with both Kajansi and Chelel clays which had be leached in 20% acid.

The content of copper in cotton oils decreased from 0.5ppm to 0.15ppm using Kajansi clay leached in 20% acid yet when Chelel clay leached under similar conditions was used decrease was from 0.5 to 0.1ppm. Similarly, the content of iron in cotton oils bleached using Kajansi clay decreased from 2.5 to 0.2 yet that bleached using Chelel clay decreased to 0.1ppm. The content of iron in sunflower oils bleached using Kajansi clay leached in 20% acid decreased from 1.6 to 0.2ppm yet that bleached with Chelel clay under similar conditions decreased to 0.1ppm.

The acid values showed that the acidity in sunflower oils is largely due to oleic acid as the average value for acids is in the range close to oleic acid, 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 showing that freshly bleached oils were fit for human consumption.