Distribution of zearalenone in malted barley fractions dependent on Fusarium graminearum growing conditions

Zearalenone (ZON) distribution was measured in main fractions of malted barley, dependent on incubation time (17, 26, 34 days), water activity (0.95 and 0.98) and temperature (20 °C and 30 °C). Malted samples were sterilised and inoculated with Fusarium graminearum. ZON levels were higher (p < 0.01) in bran and germ than flour under almost all growing conditions. Incubation at 30 °C resulted in generally lower ZON levels in germ and bran, regardless of aw and incubation time. After 34 days, ZON levels in flour from samples that were incubated at the higher temperature rose significantly. At 20 °C ZON concentration showed a bell-shaped concentration profile with increasing incubation time in bran and germ, whilst ZON levels in flour increased at aw 0.98 and dropped at the lower aw. The results indicate the importance of storage conditions for ZON levels in commercially relevant grain fractions of malted barley and help predict existing mycotoxin levels or manipulate storage conditions to reduce ZON content.