Refined red palm olein (RPOo) is the first cooking oil that is a pro-Vitamin A source due to its high carotenoid concentration. The quality specifications from the manufacturers are usually applied to freshly produced oil. However, there is currently no information regarding the oxidative stability and phytonutrient content (Vitamin E and Carotene) for RPOo after prolonged storage time. The objective then is to study the effect of two local storage conditions and storage period(s) on the oxidative stability of RPOo. In this study, peroxide value (PV), p-anisidine value (AnV), induction period (IP), free fatty acid (FFA), and Vitamin E content were determined periodically for twelve months under local storage conditions (supermarket and kitchen). Carotene content, however, was determined only at initial and at the 12th month of storage time periods. It was found that there was an overall progressive but slow increase in PV and p-AnV. For PV, the storage effects were inconsistent. However, the effects were significant (p < 0.01) on the AnV throughout storage. At the end of the 12-months, for both storage conditions, the PV < 10 meq O2 g-1, the AnV < 10, the FFA < 0.2 % (palmitic acid), with a 30% drop in the total Vitamin E, and carotenoids content showed no significant drop (p < 0.01). The PV and AnV were also within Codex Alimentarius' recommended limits. Finally, the oxidative parameters showed that RPOo remains stable after year storage under the two simulated local storage conditions (the aforementioned supermarket and kitchen).
Extending the frying-life of oils is of commercial and economic importance. Due to this fact, assessment on the thermal stability of frying oils could provide considerable savings to the food processors. In this study, the physico-chemical properties of five palm products mainly palm oil, single-fractionated palm olein, double-fractionated palm olein, red palm olein and palm-based shortening during 80 hours of heating at 180 degrees C were investigated. Heating properties of these products were then compared with that of high oleic sunflower oil, which was used as reference oil. The indices applied in evaluating the quality changes of oils were free fatty acid, smoke point, p-anisidine value, tocols, polar and polymer compounds. Three palm products i.e. palm oil, single-fractionated palm olein and double-fractionated palm olein were identified to be the most stable in terms of lower formation of free fatty acid, polar and polymer compounds as well as preserving higher smoke point and tocols content compared to the other three oils. The low intensity of hydrolytic and oxidative changes due to prolonged heating, suggests that these palm products are inherently suitable for frying purposes.
Sixty-four bottles of red palm olein and palm olein (constituted as control) samples were stored at permutations of common home setting variables which are: temperature (room temperature (24°C) or 8°C), light (kept in dark or exposure under light) and oxygen (opened or sealed caps). The effects of temperature, oxygen and light on the stability of red palm olein and palm olein were studied over 4 months of storage at simulated domestic conditions. The degree of auto- and photo-oxidations was evaluated by monitoring the following quality parameters: acidity, peroxide and p-anisidine values, fatty acids composition, carotenes and vitamin E. It is noted from the study that opened bottles of red palm olein was found to be stable for 4 months in comparison to its counterpart (palm olein) evidenced from their primary oxidative constituents (peroxides) and hydrolytic behavior (free fatty acids). Opened bottles are better off when stored at 8°C and protected from light for a longer shelf-life. Sealed bottles of palm olein showed better storage stability in the dark at 8°C; whereas sealed bottles of red palm olein was found to be stable at both temperatures studied without the influence of light. After 4 months of varying storage conditions, the fatty acid composition, vitamin E and carotenes of both oils remained unchanged. The phytonutrients in red palm olein rendered better storage stability when compared to palm olein.
In order to overcome the stability problems of oils and fats, synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) have widespread use as food additives in many countries. Recent reports reveal that these compounds may be implicated in many health risks, including cancer and carcinogenesis. Hence, there is a move towards the use of natural antioxidants of plant origin to replace these synthetic antioxidants.
The study was designed to evaluate the nutritive value, thermal stability and consumer acceptance of cupcakes baked with red palm olein compared to palm olein. Thermal stability was evaluated for acidity, peroxide, p-anisidine and total oxidation value (cumulative between peroxide and p-anisidine values), as well as fatty acid composition. The concentrations of phytonutrients including tocopherols and tocotrienols, alpha- and beta-carotene after baking were also determined. Acceptance of the cupcakes was assessed using a structured hedonic scale of five points by 29 panelists. As compared to initial test oil (red palm olein), acidity (red palm olein, 0.07±0.01% vs cupcakes containing red palm olein, 0.09±0.01%; P=0.0232), peroxide value (red palm olein, 0.33±0.05 meq O2 kg-1 vs cupcakes containing red palm olein 0.73±0.06 meq O2 kg-1; P=0.0011) and total oxidation value (red palm olein, 2.24±0.13 unit vs cupcakes containing red palm olein, 3.09±0.17 unit; P=0.0012) were found to be higher in cupcakes containing red palm olein, which is within the acceptable rancidity range (peroxide value < 7.5 meq O2 kg-1) for snack food category. No changes were found on oxidative parameters (acidity, peroxide, p-anisidine values and total oxidation value) in cupcakes containing palm olein. Cupcakes made with red palm olein retained nearly 100% of alpha- and beta-carotenes upon baking. Tocopherol homologues were stable in both comparisons, with 95% retention as compared to tocotrienol homologues (~85%). Cupcakes made from red palm olein received higher score (mean=3.29) in sensory evaluation as compared to cupcakes containing palm olein (mean=3.07). The study, therefore, encourages the inclusion of red palm olein in the formulation of bakery products.