Post harvest processing used by farmers impact Ochratoxin A occurrence in coffee cherries in Côte d’Ivoire

In this study, we analysed the occurrence of ochratoxin during post-harvest processing of coffee cherries. The stripping method was used to harvest a mixture of cherries presenting different state of ripening. Cemented, tarpaulin and bamboo surfaces were used to dry the coffee cherries. Ochratoxin produced by fungal strains was extracted and assayed by HPLC using fluorescence detector and C18 column. Moreover, the level of fungal contamination in stored and non-stored coffee cherries was evaluated using DG18 plate agar. The results showed that coffee cherries were mainly contaminated with yeasts and Aspergillii notably ochre, black and green Aspergillii as well as Penicillia and Fusaria. Yeasts were highly present in freshly harvested cherries with a contamination rate (>85 %) and a load of 6.43 ± 1.59 log CFU/g whereas filamentous fungi were very low (<15% and 4.02 ± 0.06 log CFU/g). OTA content yielded in these freshly harvested cherries was 1.5 μg / kg. This trend typically changed in four days-stored cherries in which, yeasts contamination drastically decreased to less than 5 % and fungi particularly black Aspergillii sharply increased to 40-50 %. Hence, OTA production in stored cherries increased 5-folds comparatively to OTA production in non-stored cherries. At the end of the drying process the fungal contamination rate generally increased and the highest contamination rate was observed with black Aspergillii (16 folds), on bamboo drying surface corresponding to the highest OTA production. Overall, this study showed that storing coffee cherries before drying enhanced significantly the occurrence of OTA producing strains during the post-harvest processing and then black Aspergillii might be the main fungal strains involved in OTA production in coffee in Côte d’Ivoire. Keywords: Ochratoxin, Coffee cherries, storage, drying, fungal strains, Côte d’Ivoire.