Zearalenone risk in European wheat

Abstract

Zearalenone is an oestrogenic mycotoxin produced by several Fusarium species which can infect cereals, in particular wheat and maize. The predominant species responsible for zearalenone production is Fusarium graminearum, which also produces the trichothecene mycotoxin, deoxynivalenol. The infection and subsequent mycotoxin production by Fusarium spp. is largely dependent on rainfall at flowering and before harvest. High concentrations of zearalenone in particular, appear to be produced during delayed wet harvests. There has been a recent and ongoing increase in F. graminearum incidence resulting in increased occurrence of deoxynivalenol and zearalenone across northern Europe, where delayed wet harvests are more common. Zearalenone contamination of grain is largely restricted to the outer layers of wheat grain and therefore is partitioned into the bran fraction during milling. This results in higher concentrations of zearalenone in high fibre cereal products. After the delayed wet harvest in the UK in 2008, 29% of wheat at harvest exceeded the European limit for unprocessed cereals of 100 µg/kg. This resulted in difficulties in sourcing bran which would allow production of high fibre breakfast cereals within zearalenone limits and the European Commission provided a temporary derogation for high fibre breakfast cereals of 100 µg/kg zearalenone until 31 October 2009. Rainfall data and zearalenone concentrations in UK wheat from the last ten years were used to predict the occurrence of high zearalenone in wheat (10% or more of unprocessed wheat greater than 100 µg/ kg zearalenone). High zearalenone was predicted to occur one year in five for northern Europe which matches the observed incidence for the UK within the last ten years. As a consequence, current legislative limits for zearalenone in cereals and cereal products could impact on the availability of high fibre cereal products one year in five.