Effect of Storage Time at Ambient Temperature on pH and Iodine Value of Palm Oil and Groundnut Oil

Abstract

The study was carried out to investigate the effect of storage time at ambient temperature on pH and iodine value of palm oil and groundnut oil using appropriate standard methods. The iodine value of palm oil decreased from 45.69 ± 0.01^a to 45.11± 0.00^k while that for groundnut oil decreased from 56.72 ± 0.01^a to 56.22 ± 0.01^k during the period of storage indicating loss of unsaturation due to oxidation. On the other hand, the pH of both palm and groundnut oils showed a more impressive decrease from 6.85 ± 0.05^a to 4.19 ± 0.00^j and 6.40 ± 0.00^a to 4.40 ± 0.00^h., respectively, due to autoxidation of the oils. A trend of decreasing order of iodine and pH value as the number of days of storage increases for both oils (palm and groundnut oil) was observed. This study shows that the storage time has a high significant effect on the iodine Value and pH value of both oil (palm and groundnut oil) with p ˂ 0.00 as against p ≤ 0.05. It was also observed that there was loss of unsaturation in both oils but higher in palm oil. However, groundnut oil had a higher iodine value, implying that groundnut oil had more of unsaturated fatty acid than palm oil which tends towards saturation due to high level of decreasing iodine value. However, from literature, it has been stated that groundnut oil is likely to be healthier for consumption due to the presence of unsaturated fat it contains.