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The enzymatic properties of brewing malts are an important and sometimes limiting factor in malt and beer production. In order to observe malt quality, multiple analytical tests were developed for ...

Fusarium 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 unde...

Fusarium head blight (FHB) is a significant fungal disease of barley implicated in various brewing-related disorders and could further influence the expression of genes related to malting quality. The aim of our research was to improve understanding of barley gene regulation in FHB-infected grain over time, starting from the onset of infection on flowering spikes, right up to preparation of finished malt. Two two-rowed spring barley varieties (Grace and Scarlett) were infected with species-specific spore suspensions of Fusarium culmorum , Fusarium avenaceum , Fusarium langsethiae , or Fusarium sporotrichioides under greenhouse conditions. We selected a subset of barley gene candidates related to plant defense and to malting quality traits for our gene expression analyses. We further complemented this by measuring the Fusarium DNA content in the same samples. Our work demonstrates that gene expression is indeed altered by Fusarium infection both before harvest and during malting. This includes increased expression of plant defense genes and differential expression of malting-related genes, in particular the two β -amylase genes, α-amylase and α-amylase/trypsin inhibitor. This research increases the understanding of transcriptional changes in barley grain in response to different Fusarium species and emphasizes the importance of Fusarium control before harvest for securing high quality malt.

Fusarium spp. are ubiquitous field pathogens, which are known to affect quality characteristics of cereals. Infections with Fusarium pathogens in brewing cereals are problematic and augur for a poor malt quality. The negative effects of Fusarium infections are various. Besides causing agronomic losses, kernel discoloration, and the production of several mycotoxins, Fusarium spp. are known to enhance the proteolytic activity of infected barley malt. Enhanced proteolysis can be observed in higher values in free amino nitrogen (FAN) as well as in soluble nitrogen. Previous studies showed that, in recent crop years, the predominant Fusarium spp. detected in European malt was F. avenaceum. This study focuses on the changes in the albumin fraction during the malting process of barley samples artificially infected with F. avenaceum in comparison to uninfected control samples. The barley samples were grown under controlled conditions in a greenhouse, and two different sample types were studied: One was not infected with Fusarium spores whereas the other sample was inoculated during anthesis with a spore suspension of F. avenaceum. Malting trials were carried out in a micromalting facility under defined conditions. To monitor the changes in protein profiles due to Fusarium infection, samples were analyzed at different stages of the malting process: barley (raw grain), poststeeping, postgermination, and postkilning. To evaluate the changes in the protein composition, different fractionation techniques (Osborne fractionation, isoelectric focusing, and capillary gel electrophoresis) were utilized. The albumins of the Osborne fractionation were further analyzed as they represent the main metabolically active proteins. Protein maps of the different malting steps were plotted with a custom-programmed visualization tool for comparing the infected and uninfected samples at each malting step. The results elucidate the changes in the albumin fraction during the malting process and reveal the influence of Fusarium infection on the albumin composition of barley, barley malt, and the intermediate products of malting.

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.