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 μl), 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.