A study on fungal populations and their toxins associated with coffee beans

Abstract


Fardos Bokhari* and Magda Mohammad Aly

Thirty samples of coffee beans were collected from different places of Jeddah, Saudi Arabia to determine and identify fungal population. Twenty six species belonging to 7 genera were isolated using potato dextrose agar (PDA) and malt extract agar (MEA) media at 28°C. The most prevalent genera were Aspergillus and Penicillium. Aspergillus was present in 73 and 100% of the samples but Penicillium was present in 86.6 and 100% on the two mentioned media, respectively. Also, Fusarium, Mucor, Rhizopus and Alterneria were recovered in moderate incidences on the two media. Out of the thirty samples of coffee beans collected, thirteen were contaminated with mycotoxin (43.3%). Mycotoxin profiles were also determined in these samples. It was found that aflatoxin G1 (Afl G1) showed the highest incidence rates of occurrence. It occurred in about 23.3% of all samples analyzed and in 54% of the mycotoxin contaminated samples. The other toxins detected were aflatoxins B1 (16.6%), B2 (10%), G2 (6.6%), ochratoxin (10%), patulin (16.6%) and sterigmatocystin (6.6%). The factors affecting the Afl G1 production by Aspergillus flavus were studied. The results clarified that addition of caffeine up to 1 g/l reduced the toxin synthesis (Afl G1) . The effect of some medicinal plants and spices added singly or in combination to the malt extract, on fungal growth and AflG1 production by A. flavus was also studied. Cinnamon and cloves affected fungal growth and mycotoxin production. No growth or toxins were detected in the presence of the two plants. Saffron and ginger did not affect fungal growth or prevented toxin production by A. flavus. In conclusion, coffee beans in Saudi Arabia are highly contaminated with toxigenic fungi, specially, A. flavus, which was found in this study to be the main producer of Afl G1. Medium, temperature, vitamin C, caffeine and some medicinal plants or spices which are used as a traditional additive in Saudi Arabia may affect fungal growth or/and toxin production

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