Aberrant Behavior of Deoxynivalenol Production in the Malting of Fusarium Head Blight Infected Barley: Mycotoxin Accumulation and Hyphal Localization in Single Kernels

Abstract

The malting industry faces a dilemma in which barley, initially containing low deoxynivalenol levels, occasionally exhibits an unexpected increase in deoxynivalenol levels during malting. In the current study, we investigated mycotoxin accumulation and hyphal localization in single kernels from Fusarium head blight infected barley and malt samples which showed an aberrant behavior of deoxynivalenol increases during malting. While deoxynivalenol levels in these bulk barley samples already ranged from <0.20 to 1.27 µg/g, they further increased on average by approximately 500% after malting, along with Fusarium growth. In addition, deoxynivalenol-3-glucoside and 3-acetyl deoxynivalenol levels increased from <0.20 µg/g to the mean levels of 2.47 µg/g and 1.03 µg/g in the bulk malt, respectively. In the investigation of single kernels, results showed that only 7% of barley single kernels (n = 385) had deoxynivalenol >1.00 μg/g, with the maximum level of 35.97 μg/g. However, 31% of malt single kernels contained deoxynivalenol >1.00 μg/g and up to 255.43 μg/g. Deoxynivalenol-3-glucoside and 3-acetyl deoxynivalenol were found in 40% of malt single kernels. Fungal hyphae were observed in the aleurone layer and embryo of barley kernels with deoxynivalenol >10.00 μg/g, in addition to the husk and vascular bundles of kernels with deoxynivalenol <1.00 μg/g. Hyphae spread largely in these tissues following malting, and even into the endosperm and pericarp cavities of extremely high deoxynivalenol kernels (i.e., >100.00 μg/g).