Effect of Heat on the Physicochemical Properties of Groundnut Oil

Oil was extracted from fresh groundnut seeds (used as control) and groundnut seeds heated at 90 0C and 120 0C, and market roasted groundnut seeds (fried and bottled seeds purchased from a local market) using n-hexane. The various oil samples were analyzed for their relative densities, viscosities, refractive indices, iodine values and peroxide values. Results obtained show that oxidative rancidity of the oil samples increased with increase in temperature the seeds were subjected to. Relative density increased from 0.9115 0.0005 (for oil from fresh groundnuts) to 0.9241 0.0002 (for oil from the market roasted sample). The viscosities of the various samples also showed an increase from 33.02 M2S-1 (for oil from fresh groundnuts) to 61.6 M2S-1 (for oil from the market roasted seeds). A similar trend was observed for other parameters refractive index decreased from 79.9470g/100g to 59.6430g/100g while peroxide values increased from 1.8mEq/kg to 7.6mEq/kg. The oil sample obtained from the market roasted seeds recorded the highest level of oxidative deterioration.