Fungal Contamination and Aflatoxin B1 on Postharvest Coffee Beans in North Sumatera, Indonesia

The aim of the paper is to observe aflatoxin contamination and toxigenicity of Aspergillus flavus in relation to soil at plantations and coffee beans during drying and storage at smallholder plantations in Berastagi, Karo Regency, North Sumatra. Serial dilution and a direct plating method were used to determine the fungal population and the percentage of beans infected by fungal species. Toxigenicity of A. flavus was tested using a culture method and thin-layer chromatography. The results showed a total of 18 species of fungi were isolated from the soil plantation. Aspergillus niger was the most dominant (log 3.69 cfu/g), followed by A. flavus (log 3.47 cfu/g) and A. tamarii (log 3.43 cfu/g). Cladosporium cladosporioides, Rhizopus stolonifer, and Mucor sp. contaminated the coffee beans during drying, while Aspergillus chevalieri, A. niger, A. repens, A. terreus, and Penicillium citrinum contaminated the beans during storage. The highest percentage (15%) of beans contaminated during drying was caused by R. stolonifer and Mucor sp., whereas during storage, A. niger (15.5%) was the dominant contaminant, followed by A. flavus (14%). A total of eleven A. flavus strains were isolated, consisting of three strains from the plantation, seven strains from coffee beans during drying, and one strain from storage. Based on toxigenicity, 10 strains of A. flavus were aflatoxin producers, with three strains isolated from the soil, six strains isolated from coffee beans during drying, and one strain isolated during storage.