Little is known about the fate of Fusarium mycotoxins during the barley malting process. To determine the fungal DNA and mycotoxin concentrations during malting, we used barley grain harvested from field plots that we had inoculated with Fusarium species that produce type A or type B trichothecenes or enniatins. Using a recently developed multimycotoxin liquid chromatography-tandem mass stable isotope dilution method, we identified Fusarium-species-specific behaviors of mycotoxins in grain and malt extracts and compared toxin concentrations to amounts of fungal DNA in the same samples. In particular, the type B trichothecenes and Fusarium culmorum DNA contents were increased dramatically up to 5400% after kilning. By contrast, the concentrations of type A trichothecenes and Fusarium sporotrichioides DNA decreased during the malting process. These data suggest that specific Fusarium species that contaminate the raw grain material might have different impacts on malt quality.

A detailed study on the degradation of iso-α-acids was conducted. Because of the complexity of the wort matrix and interfering interactions during real wort boiling, the investigation of degradation kinetics was performed in an aqueous solution. Degradation was investigated as a function of time (0-90 min), temperature (80-110°C), pH value (4-7), original gravity (10-18°P) and ion content of the water (0-500 ppm Ca 2+ and Mg 2+ ). After 90 min of boiling, over 20% of the dosed iso-α-acids could no longer be detected. A strong dependence of degradation could be shown due to high temperature, low pH, high original gravity and a high Mg 2+ content. The cis:trans ratio and co-iso-α-acid content did not change significantly. Losses of isohumulones could be lowered by reducing the temperature and original gravity, as well as by heightening the pH value. High amounts of Ca 2+ and Mg 2+ salts also led to an increase in degradation products. Solutions to decrease degradation and thereby possible improvements in sensory bitter quality are discussed.

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Some information is available about the fate of Fusarium toxins during the brewing process, but only little is known about the single processing steps in detail. In our study we produced beer from two different barley cultivars inoculated with three different Fusarium species, namely, Fusarium culmorum, Fusarium sporotrichioides, and Fusarium avenaceum, producing a wide range of mycotoxins such as type B trichothecenes, type A trichothecenes, and enniatins. By the use of multi-mycotoxin LC-MS/MS stable isotope dilution methods we were able to follow the fate of Fusarium toxins during the entire brewing process. In particular, the type B trichothecenes deoxynivalenol, 3-acetyldeoxynivalenol, and 15-acetyldeoxynivalenol showed similar behaviors. Between 35 and 52% of those toxins remained in the beer after filtration. The contents of the potentially hazardous deoxynivalenol-3-glucoside and the type A trichothecenes increased during mashing, but a rapid decrease of deoxynivalenol-3-glucoside content was found during the following steps of lautering and wort boiling. The concentration of enniatins greatly decreased with the discarding of spent grains or finally with the hot break. The results of our study show the retention of diverse Fusarium toxins during the brewing process and allow for assessing the food safety of beer regarding the monitored Fusarium mycotoxins.

Cereal Chem. 94(4):659-669Fusarium infections in malting barley cause mycotoxin contamination, quality impairment, and processing difficulties. The visual assessment of barley malt is a commonly applied practice in the malting and brewing industry to screen cereal batches for fungal infection, because it assumes a direct connection between occurring symptomatology and actual fungal contamination. The exceedance of a defined limit of red kernels (usually five to seven) in a 200 g subsample of malt is associated with an unjustifiable risk for further processing and can lead to reductions in price or the rejection of the entire batch. The present study evaluated the suitability of this method to ensure product quality and safety. It was further intended to resolve the presumed linkage between kernel discoloration and Fusarium infection. In general, symptomatology showed low predictability for Fusarium contamination. However, significant correlations became apparent between the number of discolored kernels and fungal DNA contents under conditions of higher levels of infection, although this was not the case for mycotoxin levels. Although symptomatology is likely overinterpreted in regard to its reliability as an indicator for Fusarium contaminations, it might still assist in assessing the risk of certain fungal contaminants. † Corresponding