Investigations into selected mycotoxins in barley, malt and wheat

Abstract

The aims of this project were to survey the incidence in UK cereal grain of certain mycotoxins which have been identified as potential concerns for European cereals and cereal products. These mycotoxins include diacetoxyscirpenol (DAS), neosolaniol, fusarenon-X, T-2 and HT-2, all of which are produced by Fusarium species, and citrinin, which is produced by certain Penicillium moulds, often in conjunction with ochratoxin A. In addition, the project investigated the potential for formation and / or degradation of these mycotoxins during malting and brewing.

Representative sample sets of barley (malting and feed), milling wheat and feed oats from the 2004 and 2005 harvest were analysed. Results suggest that the Fusarium mycotoxins neosolaniol, fusarenon-X and diacetoxyscirpenol were currently very rare in UK grown grain. The incidence of T-2 and HT-2 toxins appeared to be increasing in all cereals, but concentrations remained low, except in oats. Citrinin was not detected very frequently. However, there would appear to be a significant risk of its formation in grain which is not stored correctly.

The potential for mould growth and toxin formation during malting was investigated using artificially infected barley which had been inoculated with toxigenic moulds and held under high moisture and temperature conditions in order to encourage mould growth. The infected barley was then malted immediately. These conditions are obviously not meant to simulate commercial grain storage or commercial malting practice but were required to provide sufficient levels of infection to allow the toxins to be monitored during processing.
 
Results suggest that if viable mould capable of producing nivalenol or deoxynivalenol were present on barley used for malting, it is possible that mycotoxin concentrations could rise during malting. Only limited loss of these mycotoxins was observed during malting, but losses might be expected to be higher under commercial conditions, where concentrations of viable mould would be substantially lower.
 
In contrast, significant losses of fusarenon-X, neosolaniol, diacetoxyscirpenol, T-2 toxin and citrinin were observed during malting, even in the presence of large amounts of viable toxigenic mould. Under commercial conditions, with less mould inocula, it is probable that significant quantities of HT-2 would also be lost during malting.

Malts containing high levels of mycotoxins were brewed on the pilot scale. Brewing performance and beer quality were noticeably affected. Substantial proportions of deoxynivalenol, nivalenol, fusarenon-X and neosolaniol persisted into the final beer. However, significant losses of T-2, HT-2 and diacetoxyscirpenol were observed.