Phenotypic Characterization of Mycotoxigenic Fungi Isolated from Palm Oil Sold Within Bauchi Metropolis, Nigeria

Abstract

Background and Aim: Palm oil is widely consumed in Nigeria, but poor handling, storage, and marketing conditions predispose it to fungal contamination and mycotoxin production, posing public health risks. This study aimed to phenotypically characterize mycotoxigenic fungi isolated from palm oil sold within Bauchi metropolis and assess their fungal load as well as the physicochemical quality. Place and Duration of Study: The study was carried out in Bauchi Metropolis, Bauchi State, Nigeria, using palm oil samples collected from Wunti, Muda Lawal, Central, and Yelwa markets. Laboratory analyses were conducted at the Microbiology Laboratory, Abubakar Tafawa Balewa University (ATBU), Bauchi. Methodology: A total of 100 palm oil samples were randomly collected (25 per market). Fungi were isolated using the direct plating method on Potato Dextrose Agar supplemented with chloramphenicol. Phenotypic identification was based on macroscopic and microscopic characteristics. Fungal load was determined using the colony-forming unit (CFU/g) method. Physicochemical properties (density, viscosity, color, tactile quality, and moisture content) were analyzed using AOAC standard procedures. Results: Seven fungal taxa were identified, with Fusarium species showing the highest prevalence (42.5%), followed by Aspergillus niger (17.5%), A. parasiticus (12.5%), A. flavus (10.0%), Penicillium species (10.0%), A. fumigatus (5.0%), and Mucor species (2.5%). Mean fungal loads ranged from 3.1 × 10⁶ to 1.0 × 10⁷ CFU/g, exceeding recommended microbial limits for edible oils. Physicochemical parameters largely fell within acceptable standards, though variations suggested differences in handling and storage practices among markets. Conclusion: Palm oil sold in Bauchi metropolis is contaminated with potentially mycotoxigenic fungi, particularly Fusarium and Aspergillus species, at levels that may pose health risks. Although physicochemical quality was generally acceptable, high fungal loads indicate poor hygienic practices. Improved processing, storage, and regulatory monitoring are necessary to ensure consumer safety.