Abstract
Coffee bean-contaminating fungi were determined in random samples collected in Riyadh, Kingdom of Saudi Arabia, using the direct plating technique. Forty-five samples were examined and 12 fungal species belonging to 5 genera were isolated. Aspergillus niger was the most widely distributed and most frequently isolated fungus (86.67%). The ability of the predominant fungus, A. niger, to produce oxalic acid was evaluated using high-performance liquid chromatography. About 50% of the tested A. niger isolates produced oxalic acid; the amount produced was in the range of 90-550 ppm of oxalic acid. Because A. niger was the predominant and most widely distributed toxigenic fungus in the examined samples, more efforts should be directed to minimize the risk of oxalic acid contamination of commoditized coffee beans in the Kingdom of Saudi Arabia.