2. Materials and methods
Experimental design
To determine the effect of water activity (aw), storage temperature and elevated
levels of carbon dioxide in the presence of various levels of oxygen simultaneously
on the growth of, and aflatoxin production by Aspergillus flavus in peanuts, a
3-factor, 5-level central composite rotatable design (CCRD) of Box et al. (1978)
was used (Table 1). The range of levels of each factor used in the study included
a w (0.91-0.97), temperature (16.6-33.4°C) and headspace oxygen (1.6-18.4% v/v)
in a balance of carbon dioxide and nitrogen (60:40% v/v). The values of each
level of environmental factor selected were based on previous studies with A.
flavus (Diener and Davies, 1970; Landers et al., 1967; Northolt et al., 1977; Shih
and Marth, 1973; Ellis et al., 1993a). The actual values of levels used in the CCRD
are shown in Table 1, as described by Khuri and Cornell (1987). All experimental
runs were replicated three times.