The influence of modified atmospheres and their interaction with water activity on the radial growth and fumonisin B1 production of Fusarium verticillioides and F. proliferatum on corn. II. The effect of initial headspace oxygen concentration
2007
Samapundo, S. | Meulenaer, B de | Atukwase, A. | Debevere, J. | Devlieghere, F.
This paper is the second in a series of two that describe the effect of modified atmospheres on the growth and mycotoxin production of Fusarium verticillioides and Fusarium proliferatum on corn. In this part, the effect of initial headspace (IH) oxygen concentration and its interaction with water activity (a(w)) on growth and fumonisin B1 production was investigated. In addition, the impact of vacuum packaging and in-cooperation of O2 scrubbing sachets was also studied. It was observed that at all aw values studied, reduction of IH O2 concentration from 20 to 2% had no significant effect on the colony growth rate (g, mm d-1) and lag phase duration (λ, d). However, g and λ were positively and negatively correlated to a(w). The IH O2 concentration was determined to have a a(w) dependent effect on the oxygen consumption rate. Although the maximum colony diameter (D(max), mm) decreased with the reduction of the IH O2 level, the greatest mycelial density occurred at 10% IH O2 for both isolates. This observation was accompanied by a trend of a decrease in the value of the IH O2 level at which the most fumonisin B1 was produced from 15 to 5% when the a(w) was decreased from 0.976 to 0.930 for F. verticillioides. For F. proliferatum the optimum conditions for fumonisin B1 production shifted from 20% at a(w) 0.976 to 10% at both 0.951 and 0.930. Vacuum packaging and the in-cooperation of O2 absorbing sachets completely inhibited the growth of both isolates. These results together with those reported in Part I of the study indicate that O2 should preferably be completely excluded from modified atmospheres that are employed to protect stored corn from fungal growth and mycotoxin production.
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