Cyanide influence on the growth of mycotoxigenic fungi from cassava flour in vitro

The hypothesis that residual cyanide present in cassava flour influences the growth of mycotoxigenic Aspergillus was established. Therefore, cyanide concentrations were measured in three types of flour: mixed, dry and watery (n=30), as the basis for the establishment of doses to be used. Fungi sowing were performed in solid Saboraud medium with a central well (500 μL), in which 5, 10, 15 and 20 mg CN kg-1 concentrations were applied, and control group was established using distilled water (0 mg CN kg-1). Plates were incubated at 25°C for 24, 48 and 120 h and evaluated on direct observation of fungal growth. Results showed that fungi grown unevenly according to the applied concentration. The initial development at all concentrations, in both genera, was by the edge of plates, at a slower rate in larger doses. After 120 h only the 20 mg kg-1 concentration did not grow near the center circle. Thus, results show that cyanide slows fungi growth of mycotoxigenic Aspergillus flavus assessed, with dose-dependent effect. It is important to apply the good practices in cassava flour production in order to control cyanide levels, as well as the reduction of toxigenic fungi, to promote the food safety.