Impact of pre-harvest rainfall on the distribution of fusarium mycotoxins in wheat mill fractions

Legislative limits for Fusarium mycotoxins decrease from unprocessed wheat to processed products. A previous observational study identified a seasonal difference in the distribution of deoxynivalenol (DON) but not zearalenone (ZON) within mill fractions. Rainfall is known to influence the production of these mycotoxins in wheat, but the effects of rainfall on their distribution within mill fractions is not known. Laboratory and field experiments were conducted to determine the impact of different watering regimes on the distribution of DON and ZON in wheat mill fractions. Results indicated that repeated wetting and drying could cause movement of DON towards equilibrium across the mill fractions. Whereas, high levels of rainfall could cause a large reduction of DON in the grain, predominantly from the bran fraction, resulting in a proportional increase within white flour. ZON was detectable in fewer samples but results indicated it is less mobile within the grain. It is important for processors to be aware of the variation of mycotoxin distribution within mill fractions and the drivers of this variation to ensure limits set for grain intake result in mill products within mycotoxin legislative limits

Testing cereals for mycotoxins Review and assessment of rapid test kits

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Distribution of Fusarium mycotoxins in UK wheat mill fractions

The EU has set maximum limits for the Fusarium mycotoxins, deoxynivalenol (DON) and zearalenone (ZON). The maximum permitted level decreases from unprocessed wheat, through intermediary products, e.g. flour, to finished products such as bakery goods and breakfast cereals. It is, therefore, important to understand the effects of processing on the mycotoxin distribution in mill fractions. Between 2004 and 2007, samples were taken at commercial flour mills at various points in the milling process and analysed for trichothecenes and ZON. Samples with a range of mycotoxin concentrations harvested in 2004 and 2005 were processed in a pilot mill and the mycotoxins in the different mill fractions quantified. In the commercial samples, DON was the predominant mycotoxin with highest levels detected in the bran fraction. Analysis of the pilot mill fractions identified a significant difference between the two years and between mycotoxins. The proportion of DON and nivalenol in the mill fractions varied between years. DON and nivalenol were higher in flour fractions and lower in bran and offal in samples from 2004 compared to samples from 2005. This may be a consequence of high rainfall pre-harvest in 2004 resulting in movement of these mycotoxins within grains before harvest. There was no significant difference in the distribution of ZON within mill fractions between the two years. For DON, higher concentrations in the grain resulted in a greater proportion of DON within the flour fractions. Understanding the factors that impact on the fractionation of mycotoxins during milling will help cereal processors to manufacture products within legislative limits