Microbial Contamination in Traditional and Semi-Mechanized Palm Oil Processing in Nigeria

Abstract

Palm oil is widely used edible oil in Nigeria, processed through both traditional (manual) and semi-mechanized methods. However, microbial contamination during processing and storage raises significant concerns regarding food safety and industrial microbiology. This study evaluated the microbial quality of manually processed palm oil from Oju, Benue State, and semi-mechanized processed palm oil from Agbor, Delta State. A total of twenty-seven (27) palm oil samples were aseptically collected from 12 traditional processors and 15 semi-mechanized processors. Isolation and enumeration of microorganisms were performed using Nutrient Agar, MacConkey Agar, and Mannitol Salt Agar for bacteria, while Sabouraud Dextrose Agar was used for fungi. Microbial counts were reported in CFU/mL. Bacterial identification was carried out based on biochemical, cultural, and morphological characteristics, while fungal identification involved macroscopic and microscopic analysis. In total, 61 microbial isolates were identified, including Bacillus spp. (8), Escherichia coli (11), Staphylococcus spp. (8), Pseudomonas spp. (2), and Enterobacter spp. (2) among bacteria, as well as Aspergillus spp. (12), Mucor spp. (10), Rhizopus spp. (3), and Penicillium spp. (5) among fungi. Aspergillus spp. was the most prevalent fungal isolate (19.67%), while E. coli was the dominant bacterial isolate (18.03%), indicating fecal contamination. The total viable count (TVC) and total coliform count (TCC) for traditionally processed palm oil were significantly higher than those for semi-mechanized palm oil (p < 0.05), reflecting differences in hygiene practices and processing conditions. Although the microbial loads were within NAFDAC’s permissible limit of 2.0 × 10? CFU/mL, the presence of multiple microbial species exceeded regulatory thresholds. These findings highlight the need for strict hygiene regulations, improved microbial monitoring, and enhanced processing practices to ensure food safety and maintain industrial quality standards in Nigeria’s palm oil industry. Further research on microbial control strategies is recommended to reduce contamination risks and improve product stability.