EFFECT OF EXTRACTION METHODS ON YIELD AND QUALITY CHARACTERISTICS OF COCONUT (Cocos nucifera L) OIL

Abstract

Oil extraction method has a direct influence on the quantity and quality of vegetable oil obtained from plant parts. This study aimed at evaluating the effect of three extraction methods (traditional, mechanical and chemical) on the quality characteristics (including some proximate composition, microbial content, physical and chemical properties) of the coconut oil. The experiment was laid out in a completely randomized design and data obtained were subjected to analysis of variance while the mean of each variable were compared using Duncan’s new multiple range test at 95% level of confidence. The highest average oil yield of 82.7% (±3.03) was obtained from chemical extraction method using n-hexane as solvent, mechanical extraction method gave 72.9% (± 1.49) while the lowest oil yield of 61.3% (± 2.73) was obtained from traditional extraction method. Extraction method had a significant impact on the crude protein of the coconut oil; highest crude protein content (2.39%) was obtained for mechanical extraction method while the lowest protein content 1.68 was obtained for chemical extraction method. The highest Total Titratable Acid (TTA) of 0.58±0.25 was obtained for traditional extraction method while the lowest value of 0.25±0.01 was obtained for mechanically extracted oil. The free fatty acid ranged from 1.73 to 2.21 mg KOH/g while saponification value ranged from 248.52 – 263.28 mg KOH/g for traditional and chemical extraction methods respectively. Chemical extraction method has the highest pH value of 5.1 while mechanical expression has the lowest pH value of 4.5. Also, the result shows that the extraction method has a significant difference on the Total Titratable Acid of the coconut oil. Traditional method has the highest fungal count and a higher bacterial infection was observed in mechanical method. The total microbial count of the oil samples ranged from 5.07 to 6.19 x 10² cfu/ml. The highest microbial load (6.19 x10² cfu/ml) was in the traditional oil extraction method while the least microbial count occurred in the solvent oil. Flash point ranged from 124 to 131 for traditional and chemical methods respectively, a constant specific gravity value of 0.94 was obtained for the three methods used; lowest boiling and melting point (196.33 and 41^oC) was obtained for chemical method while highest values (204 and 45^oC) were obtained for traditional and mechanical methods respectively. Extraction methods had significant influence on the yield and quality of coconut oil; the quality attributes of the oil were comparable to international standards.