Variability of deoxynivalenol measurements in barley.

Deoxynivalenol (DON), a toxin produced by Fusarium fungi, can occur in many cereal grains. If wet climatic conditions coincide with the flowering period of plant development, circumstances are favorable for the fungi infection. Because the presence of DON in barley can have significant economic consequences to barley producers, commercially available test kits are used to measure DON in shipments throughout marketing channels. The quantity of barley sampled from a lot and used to measure DON can vary widely, depending on where the test is conducted. The Grain Inspection, Packers and Stockyards Administration of the U.S. Department of Agriculture specifies that a minimum of 100 g of grain must be processed to measure DON. Other laboratories may use more or less grain. A study undertaken to measure the variability among measurements of different sample sizes found no detectable differences in variability attributable to sample size. It was concluded that the variability among DON concentrations in samples from the lot was small relative to that introduced by the measurement process (combined sample preparation and analysis). A separate experiment investigated variation among samples taken from a lot, variation among subsamples taken from ground samples, and variation among multiple replicated measurements of an extract. On 10 lots, all 3 sources were significant contributors to variation. Stratification of DON within lots was hypothesized as a source of variation of DON measurements. Tests indicated that some stratification may exist.