Study of the influence of picking frequency and drying materials on moulds and aflatoxins occurrence in cashew nuts from Côte d'Ivoire

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The aim of the present study was to evaluate the impact of picking frequency and dryers materials on fungal infection and aflatoxins content in cashew nuts produced in Côte d’Ivoire. Some cashew nuts collected after a delay of 2, 3 and 7 days on the ground, were sun-dried on racks-table, tarpaulin and cemented area to a moisture content of 8%. After 6 months of storage, 18 samples (3kg of each) of cashew nuts were collected and the fungal infection and aflatoxins content were evaluated using standard methods. Our results revealed that the rate of fungal infection evolved in keeping with the frequency of nuts picking. Thus, the rate of fungal infection was 5.7% at 2 days of frequency of nuts picking, 22.7% at 3 days and 54.6% at 7 days respectively. Proportionally, the loss rates were 1.85, 4.73 and 11.03%. The dryers had no significant effect on the infection and loss rates with corresponding values ranging from 24.49 to 31.45% and 5.41 to 10.32% respectively. A total of 12 genera and 148 fungal species were isolated and identified. The genus Aspergillus represented by Aspergillus niger (71.78%), Aspergillus flavus (4.29%), Aspergillus fumigatus (2.45%) and Aspergillus sp (1.84%) was the most preponderant. Although aflatoxin levels were marginal, they can reach 0.34 µg/kg with the 7-days pickup time. This aflatoxin level is related to the presence of aflatoxin B1 (0.29 µg/kg). The drying supports namely tarpaulins or cemented areas seemed to influence the level of aflatoxins secretion. Taken together, our results suggested that the frequency of cashew nuts picking was a critical control point in value chain for both fungal infection and aflatoxins contamination. In certain way, the racks-table seemed to be suitable drying support to avoid aflatoxins contamination.