Physicochemical Characteristics of the Oils Extracted from Some Nigerian Plant Foods – A Review

Abstract

Fats and oils are non-volatile substances insoluble in water but soluble in organic solvent. They constitute along with protein and carbohydrates, the major food stuffs and are widely distributed in nature. Oil serves as a good source of protein, lipid and fatty acids for human nutrition including the repair of worn-out tissues, new cells formation as well as a useful source of energy. Oilseeds are those seeds that contain considerably large amounts of oil. Oil can be extracted from oilseed by using traditional methods of extraction (on a very small scale), mechanical expression (hydraulic and screw presses) which can be manual, semi-automated or automated, and solvent extraction (e.g. hexane, fluid carbon dioxide) or a combination of two of these methods. Physicochemical parameters of the oils extracted from some Nigerian plant foods using standard analytical techniques were reviewed. The physicochemical properties of the plant oils reviewed  were found to be at the range concentrations as follows: Saponification value (SV): 5.58 - 249.90 mgKOH/g, peroxide value (PV): 0.45 - 290.00 mEq O₂/kg of sample, acid value (AV): 0.34 - 68.88 mg KOH/g, iodine value (IV): 2.65 - 153.00 g I₂/100g sample, density (Ds): 0.9031 - 0.9208 g/cm³, viscosity (Vs): 0.43 to 302.39 mm²/sec, specific gravity (SG): 0.830 – 1.710, refractive index (RI): 0.147 – 1.792, free fatty acid (FFA): 0.14 – 34.65 % as oleic acid, ester value (EV): 0.54 – 241.04 mgKOH/g and heat of combustion (HC): 8904.25 – 11303.35 gcal/g. The result of the reviewed work confirms the Nigerian seed oils to be of good quality and can find application either in food industry as food additives or industrial purposes such as cosmetics, soaps, paint and even energy generation.

Keywords: Physicochemical parameters, seed oils, Nigeria.