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

Abstract

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). Industrial relevance: The reduction of the incidence of F. graminearum in barley by the multi-step application of ozone in the steeping stage of the malting process is proposed as a strategy for improving the quality of malt and beer, without significant impact on barley germinative capacity and germinative energy, and reduction of water sensitivity. Shorter steeping periods are feasible, as well as the possibility of water reutilization, by these residue-free treatments.