Cereals and ochratoxin Aproducing fungi

Recent surveys of cereals from Europe, especially wheat and barley, have shown that Penicillium verrucosum is commonly isolated from cereals with A. ochraceus present only occasionally. Thus, contamination with ochratoxin A is primarily a postharvest problem. Lund and Frisvad (2003) showed that P. verrucosum contaminates grain during the harvest ing process, drying and storage. In damp harvest years in northern Europe effective drying regimes after harvest are essential to prevent P. verrucosum from becoming established. Thus, the effective management of this phase is critical to the reduction or elimination of ochratoxin A contamination in the food chain. Ambient drying systems in damp autumns require longer times for drying which may result in layers of drying grain reabsorbing moisture and being colonized by mycotoxigenic molds. P. verrucosum also is a very competitive species and can dominate under conducive environmental conditions in stored grain (Magan et al., 2003b). Some work has suggested that the level of contamination by P. verrucosum is a good indication of potential contamination by ochratoxin A (Ramakrishna et al, 1996; Lund and Frisvad, 2003; Lindblad et al., 2004). For example, Lund and Fris-vad (2003) found that samples in which > 7% of the grain was contaminated with P. verrucosum also had significant ochratoxin A contamination as well, although fungal contamination and mycotoxin levels are not linearly correlated.

Sources of infection of grain by P. verrucosum include the contaminated environments of combines, dryers, and silos. Prompt and effective drying of cereals at harvest therefore is a major critical control point for preventing the formation of ochratoxin A. In the portions of Europe where the cereal harvest is at greatest risk, measures to avoid mold and toxin problems often are effective, while in areas normally at lower risk for ochratoxin A contamination may not be adequately prepared to avoid storage problems if unusual conditions occur. For example, it may not be economical to have expensive drying machinery idle in some years, while in others the supply of damp grain may exceed the drying capacity available even though delays in drying may put the grain at risk. Another problem arises if the infrastructure lacks sufficient funds and/or expertise to ensure best storage practices are followed (Scudamore, 2003).

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