Selective effect of propionates and water activity on maize mycoflora and impact on fumonisin B-1 accumulation

The effect of a commercial mixture of propionates at two different doses (0 .05% and 0.1%) on fungal spoilage of natural maize stored at 0.85, 0.90 and 0.95 water activity (a(w),) was investigated. Parallel treatments with add ed inoculum of Fusarium Liseola section isolates (Fusarium moniliforme and F. proliferatum) were carried out in order to determine the effect of funga l interactions on the development of fumonisin-producers on maize in relati on to preservative efficacy. Fungal colonisation of grain was measured as f ungal counts (CFUs g(-1) maize). In general, no differences were found betw een inoculated and uninoculated samples. Besides the selective effect of a( w) on maize mycoflora, it was demonstrated that most genera which colonise maize remained unaffected by the preservative concentrations applied. Howev er, Penicillium populations (CFUs g(-1) maize) counts decreased significant ly. As they represent a major component of the total fungal counts, an over all control of total mycoflora was observed. Furthermore, there was a signi ficant statistical interaction between preservative and a(w) levels, with t he preservative activity enhanced at low a(w). The concentrations of fumoni sin B-1(-) were unaffected by treatment with no significant differences in concentrations found. This suggests that the natural mycoflora of maize may act as an inhibitor of Fusarium development, and consequently of fumonisin biosynthesis. (C) 2000 Elsevier Science Ltd. All rights reserved.