Multi-step ozone treatments of malting barley: Effect on the incidence of Fusarium graminearum and grain germination parameters

The effect of multi-step ozone treatments at 20 ± 1 °C in aqueous phase on the reduction of the incidence of Fusarium graminearum in artificially contaminated malting barley (104 CFU/g) was studied. Samples (50 g of infected barley) were ozonated in a bubble column that contained 500 mL water. Percentage of infected grains was assessed at three incubation temperatures (15, 20, and 25 °C). Ozonation in three steps of 45 min each (9.0 g ozone/L water per step) led to a significant reduction of the mould's incidence in barley, from 100% to 47%, 81%, and 78% at the three incubation temperatures, respectively. Germination parameters were tested separately in non-infected samples to evaluate the effect of ozone treatments on the grains' suitability for malting: germinative capacity and germinative energy were not significantly affected by the treatments (100% and 98%, respectively), whereas water sensitivity (related to the excessive absorption of water by grains, which impairs germination) was reduced from 19 to 11%. Grains treated in three steps achieved the moisture content (42%, wet basis) needed to start the germination stage in a steeping period (2.25 h) shorter than the traditional ones (36–52 h).