RELATIONSHIP BETWEENFUSARIUMINFESTATION OF BARLEY AND THE GUSHING POTENTIAL OF MALT

Abstract

Fifty barley samples, displaying a range of 0 to 100% kernels infested with Fusarium. were collected in North Dakota, South Dakota, and Minnesota during the harvest of 1994. Samples were micromalted, and the levels of the fungal metabolites, deoxynivalenol and ergosterol, were determined. Fusarium infestation and the levels of fungal metabolites were evaluated as predictors of gushing in laboratory trials. Malt samples which were infested with Fusarium or contaminated with the fungal metabolites exhibited a propensity to gush. However, only the levels of deoxynivalenol and ergosterol were found to be strongly correlated with the actual amount of gushing observed. This suggests that their production may parallel that of the component which actual causes gushing, and that screening barley and malt for these metabolites, may offer a means of reducing gushing problems in the brewery. Determination of deoxynivalenol is rapid, when it is present, and necessary because of food safety and malt quality concerns.

Fungal Hydrophobins as Predictors of the Gushing Activity of Malt

“…5). This finding is inconsistent with the results of Schwarz et al 28 who found strong correlation between the DON level and the gushing potential of malt produced from North American barley samples. Most of the samples analyzed in this study were grown in Finland.…”

“…This is probably due to the production of hydrophobins during the malting process, which could be concluded from the lower hydrophobin levels detected in the barleys compared to those of the corresponding malts (data not shown). Previous studies also support this conclusion because fungi, especially fusaria, have been shown to proliferate and to produce mycotoxins and gushing factors in the malting conditions 12,23,28,30 . Furthermore, no connection was found between the results of the hydrophobin ELISA and the deoxynivalenol (DON) contents of the malts (data not shown).…”

“…These results suggested that the three hydrophobins differed from each other to such an extent that they could not be detected with the same polyclonal antibodies. However, gushing of beer is considered to be most commonly caused by Fusarium 11,28 , which justifies the use of the F. poae hydrophobin antibodies in the ELISA test for prediction of the gushing propensity of barley and malt.…”

“…An increasing percentage of European malt samples analysed during the past five years have shown gushing tendency 1 . In the USA severe epidemics of Fusarium Head Blight in barley have occurred during the last decade, which have increased the risk of gushing 28,31 . Currently the gushing potential of barley and malt can be predicted by quantifying the presence of Fusarium fungi or their antigens 8,22,32 .…”

“…The principle weakness inherent to these methods lies in the fact that they do not directly detect the actual gushinginducing factors. Some studies have also shown that the actual Fusarium level of barley or malt is a poor predictor of gushing propensity 23,28 . The gushing test described by Vaag et al 33 and modified for barley by Aastrup 1 , relies on an aqueous extract of barley or malt being added to bottled beer so that the gushing tendency of beer can be measured after three days of shaking.…”