Abstract:
A comprehensive study was conducted on oils from raw and boiled black variety of tigernut (Cyperus esculentus L), in order to evaluate their potential uses. The quality of the extracted oils was assessed in terms of acid value, iodine value, saponification value, peroxide value, specific gravity, flash point, kinematic viscosity and unsaponifiable matter with the mean range values of 9.03-9.12 mg KOH/g, 57.30-92.60 mg of I/100 g, 179.40-180.30 mg KOH/g, 6.90-7.50 meqO2/kg, 0.90-0.91 g/cm, 275.00-282.00°C, 8.30-8.42 mm2/s at 100°C and 0.50-0.82%, respectively. The major fatty acids of the tigernut oil were oleic acid (32.14-50.85%)> linoleic acid (24.08-46.71)> palmitic acid (12.96-15.84%)> stearic acid (4.35-4.60%). Palmitoleic, eicosenoic, erucic, nervonic, elaidic, eicosadienoic, docosadienoic, α-linolenic, γ-linolenic, dihomo-γ-linolenic, eicosatrienoic, eicosapentaenoic and docosahexaenoic acids were present in small quantities with none of them recording up to 1.0% in either of the samples while lauric and myristic acids in the boiled sample were not at the detectable range of GC. The boiling process reduced the content of lauric, myristic, arachidic, behenic, palmitoleic, pentacosylic and oleic acids by 100, 100, 98.72, 99.21, 99.76, 1.47 and 36.79%, respectively. Unsaturated fatty acids predominated in all the samples with an adequate amount of essential fatty acid (linoleic acid). Generally, the boiling method showed deviations in fatty acid components from the raw sample. Phosphatidylethanolamine had the highest content (223.08 mg/100 g) in raw tigernut while the lowest was lysophosphatidylcholine (3.83 mg/100 g) also in the raw sample. However, the total phytosterols were of low values with range of 1.59e-3 to 9.74e-3 mg/100 g except that of stigmasterol and sitosterol. The high percentage PUFA and the low sterols particularly cholesterol may make processed black variety of tigernut a good food source on health wise basis.
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