Extraction and qualitative assessment of African sweet orange seed oil

  • BE Nwobi
  • O Ofoegbu
  • OB Adesina


The African sweet orange fruit Citrus Sinensis seeds were obtained from discards of fruits and prepared for use by decoating, sun drying and grinding. By solvent extraction using petroleum ether, a golden yellow coloured oil was obtained and characterized by determining the pH, refractive index, density, solvent miscibility, congealing temperature, flame nature, specific gravity, retention factor on chromatographic plate, heat of combustion, smoke point, flash point, fire point, and the percentage yield. In addition, the spectroscopic analysis was carried out using Genesis FTIR spectrophotometer. The free fatty acid, unsaponifiable matter, saponification, iodine, acid and peroxide values were determined
according to the standard method of analysis. Oil yield of 36 % was obtained. The results show a high degree of unsaturation, presence of reasonable amount of free fatty acids, marked level of oiliness, refractive index (1.47 at 25 oC), high level of acid value 82 % (0.82)—with the presence of palmitic, stearic, oleic acid, traces of linoleic acid—and interestingly, absence of linolenic, myristic and arachidic acids.
The solvent miscibility of the oil was determined by physical observation of the uniform blending of oil sample in acid (HCl), alkali (NaOH), sodium hydrogen carbonate solution, carbonate solution, ether and water at room temperature, 40 oC, 60 oC, 80 oC and 100 oC. The low value of the congealing temperature of the oil gave an indication that the oil can be handled in very many geographical regions irrespective of the difference in temperature values of such regions. The trace level content of linoleic acid of the oil confers on it a high degree of stability. The IR shows peaks at 1377.33, 1237.05, 1163.43 and 1100.14 cm-1, which are indicative of
the presence of carboxylic acids, and these are vital elemental composition of fatty acid compounds. The presence of the multiple peaks at  1100.14cm-1 in the IR chart depicts an isopropyl group presence which is also indicative of a cis–alkene groups presence, suggestive of the stable bond structure of the oleic acid family.

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eISSN: 1684-5374
print ISSN: 1684-5358