.

The antioxidative activity of turmeric extract on crude groundnut oil (CGO) was investigated. The turmeric was dried, deskinned, ground and extracted using water and ethanol. The extracts at varying concentrations were added to CGO. The refractive index (RI), free fatty acid (FFA), acid value (AV) and peroxide value (PV) of the CGO containing the extracts and 200 ppm butylatedhydroxytoluene (BHT) were determined monthly for a period of five months. The mean values of these parameters were used to compare the effectiveness of the extracts and 200 ppm BHT in preventing rancidity of CGO. The RI of the oil containing ethanol turmeric extract (ETE) and water turmeric extract (WTE) ranged between 1.4632±0.0009 and 1.4641±0.0009 respectively; and the RI of CGO containing no additive (0 ppm) and 200 ppm BHT were 1.4631±0.0011 and 1.4629±0.0013 accordingly. The FFA of CGO with turmeric extract was within 0.7311±0.1618 and 0.9400±0.1981 % oleic acid while the FFA of CGO without additive and 200 ppm BHT were 0.9400±0.1981 and 1.1228±0.2509 % oleic acid respectively. CGO containing ETE and WTE had AV ranged between 1.5586±0.3415 and 1.8703±0.3943 mg KOH/g oil; and that of CGO without additive and 200 ppm BHT were 1.9742±0.4693 and 2.2340±0.4994 mg KOH/g oil. The PV of CGO with ETE and WTE was within 13.0060±6.3654 and 21.0555±14.6185 meqO2/Kg oil while CGO that contained no additive and 200 ppm BHT were 22.9259±20.2676 and 17.8888±11.1092 meqO2/Kg oil respectively. Water turmeric extract demonstrated a better antioxidant activity than ethanol turmeric extract and 200 ppm BHT against hydrolytic and oxidative rancidity of CGO.
Keywords: Crude groundnut oil, turmeric extract, antioxidant, rancidity, oil stability