Influence of inoculum preparation and volume on growth of mycotoxigenic molds

The influence of the volume and the a(w) of the inoculum, adjusted or not with glycerol to the a(w) of the medium, on growth of mycotoxigenic species of fungi was determined for Aspergillus flavus, Aspergillus ochraceus, Penicillium citrinum, Penicillium viridicatum, Fusarium tricinctum and Microdochium nivale. Statistical analysis of the data was based on the application of multivariate techniques. It was seen that at constant volumes (10 microliter), P. viridicatum, A. ochraceus and M. nivale show no significant growth differences whether or not the a(w) of the inoculum is adjusted; but significant differences were observed with A. flavus, P. citrinum and F. tricinctum. Moreover, significant differences in growth between adjusted and unadjusted a(w) levels are also present when there are different inoculum volumes for A. flavus and P. citrinum. Thus, it is appropriate to adjust the inoculum to the same a(w) level as that of the medium or the food to be considered. In all cases, where significant differences were present, greater colony diameters were observed when the a(w) was adjusted. With the same inoculum preparation, different inoculum volumes also affect fungus growth, producing greater colony diameters with increments in the volume