EFFECT OF ADDED TOCOPHEROLS ON THE STABILITY OF PALM OLEIN AND BISCUITS CONTAINING PALM OLEIN STORED AT TROPICAL CONDITIONS

The oxidative stability of palm olein oil, with an added synthetic antioxidant, namely; Tenox 25 (T25) and two concentrates of tocopherol mixtures, namely, Covi Ox-T50 (Covi 50) and Covi Ox-T70 (Covi 70) was evaluated for 4 months storage under tropical conditions. The oxidative stability of palm olein oil stored under the aforementioned conditions was monitored by determining the conjugated dienes (CD), acid value (AV), free fatty acid (FFA), peroxide value (PV), p-anisidine value (PA), iodine value (IV) and the total oxidation value (TOTOX). The antioxidant index (AI) was also calculated. The quality of biscuits containing palm olein oil was also evaluated under the aforementioned storage conditions.
Data were analysed by the general linear analysis. Results of the oxidation measurements showed that the activity of the individual antioxidants used in the present study varied with the same type of oil, but in most of the tests, the tocopherols were as equally effective as the strong synthetic T25 and/or more superior than it in many aspects. The AI for the different antioxidants had values higher than unity and were similarly effective as T25 indicating their antioxidative powers in inhibiting the onset of rancidity in the stored oil.
Results of the quality tests of the stored biscuits indicated that the low concentrate tocopherol Covi 50 significantly (P<0.05) prevented moisture loss and rancidity development as measured by the thiobar-bituric acid number (TBA) as compared to the other antioxidants. Both added tocopherols and T25 were equally effective in preventing the pH rise of the stored biscuits as compared to the control. The sensory evaluation showed that higher scores were given by the panelists for all antioxidant treated samples with-out differentiation.