sion properties of the packaging film and storage time. Each of these factors can
significantly influence the growth of and aflatoxin production by A. flavus. Magan
and Lacey (1984) found that aflatoxigenic field and storage fungi were tolerant of
low oxygen concentrations (0.14%) and elevated carbon dioxide levels (> 15%) at
high a w levels. Conversely, the resistance of the fungi to CO 2 decreased as storage
temperature and a w decreased (Magan and Lacey, 1984). Diawara et al. (1986)
found that the biological oxygen demand was higher in stored grains with a high
initial a w, with the demand decreasing as the a w of the substrate decreased. A
similar trend was also observed for carbon dioxide production with increased
production being observed in grains stored at high aw, and a decrease in carbon
dioxide production in grains of lower a w. However, the changes in gas composition
were dependent on storage temperature (Diawara et al., 1986). Therefore, the
decrease in growth observed after weeks 1 to 2 in this present study can be
attributed to the synergistic effect of a high carbon dioxide concentration (> 55%)
produced as a result of mold metabolism, and the reduced oxygen level (< 1%) in
conjunction with storage temperature and lower a w level.