Effect of Processing Methods on the Microbial and Physicochemical Qualities of Palm Oil Produced in Ondo State, Nigeria

Abstract

This study was aimed at assessing the physicochemical and microbiological quality of Palm oil produced in Ondo State, Nigeria. Three palm oil extraction methods were used for the study. The oil samples were stored for six months, while the microbiological and physicochemical quality assessment were investigated monthly. Results show that the Free Fatty Acids (FFA), Acid Value, Peroxide Value, Iodine Value and Microbial counts of all the oil samples examined varied from one extraction method to the other over the storage period. The samples obtained through the traditional extraction methods had the least quality over the storage period. The total bacteria counts ranged from 0.66 – 3.45 x 104 cfu/ml for the mechanized, 1.25 – 4.50 x 104 cfu/ml for the semi-mechanized and 1.20 – 6.50 x 104 cfu/ml for the traditional method while the fungi count ranged from 0.30 - 5.33 x 104 sfu/ml for mechanized, 1.22 – 7.56 x 104 sfu/ml for the semi-mechanized and 2.30 – 8.56 x 104 sfu/ml for the traditional method. A range of microbes including some pathogenic, were isolated from Palm oil samples. Aspergillus flavus, Pseudomonas aeruginosa, Aspergillus saprophyticus, Varicosporum elodeae, Bacillus licheniformis, Pseudomonas aeruginosa and Staphylococcus aureus were the predominant species. However, Bacillus subtilis, Trichodema viridae and Bacillus cereus are the least isolated microorganisms. The oil extracted through the mechanized method had the lowest Free Fatty Acid (5.60 – 9.77%), Acid Value (11.20 – 20.18 MgKOH/g), Iodine Value (40.00 - 55.43 Wijs), and Peroxide Value (3.02 – 10.33 Meq/Kg) before and after storage than those extracted by the other methods. The sensory evaluation also showed preference for the palm oil extracted using the mechanized process compared to the other methods, as it retained its qualities significantly over the storage period.