Physicochemical properties and storage stability of red palm oil “Ogi”
Objective: This study determined the beta-carotene content, other physicochemical properties and storage stability of red palm oil “ogi”.
Methods: '“Ogi”' was prepared from maize and millet grains separately. Following a preliminary work, red palm oil was added to the fermented “ogi” slurry at 10% (w/v) and oven dried at 70oC for 2h, allowed to cool and milled into flour.
Results: The beta carotene content of maize and millet “ogi” increased significantly from 47.6 to 832.5 μg/100g and 416.6 to 988.5μg/100g respectively with addition of 10% (w/v) red palm oil. The added 10% red palm oil increased fat content of maize and millet “ogi” by 4 folds and in turn raised their energy levels by about 15% respectively. Ash content increased significantly from 1.2 to 2.0g/100g and 1.9 to 2.9g/100gas crude fibre increased from 0.2 to 0.3g/100g and 0.3 to 0.5g/100g while protein decreased significantly from 7.7 to 7.1g/100g and 7.8 to 7.4g/100g.Mineral elements such as zinc, iron and phosphorus increased slightly while potassium decreased for both maize and millet “ogi”respectively. Most pasting properties decreased significantly with the addition of red palm oil to “ogi”. This was accompanied by colour intensities as demonstrated by the L*, a*, b* values. After 12 weeks ambient (28±2oC) storage, peroxide values increased significantly from 0.9 to 1.9 meq peroxide/kg and 1.6 to 2.5 meq peroxide/kg while free fatty acid values increased from 7.6 to 18.9% and 7.7 to 25.3% for 10% (w/v) red palm oil maize and millet “ogi” respectively.
Conclusion: Addition of 10% (w/v) red palm oil increased the beta carotene content of “ogi” by 2 to 18 folds, improved energy levels, decreased final viscosity and enhanced the colour of “ogi”. However, the stability of the product during ambient storage decreased with time due to the onset of lipid oxidation.
Keywords: Red palm oil, “ogi”, Beta carotene, Maize, Millet