Impact of Fusarium culmorum infection on barley malt protein fractions, brewing process, and beer quality

Technical Session 10: Microbiology I Session
Pedro Oliveira, University College Cork, Cork City, Ireland

ABSTRACT: Malt infected with Fusarium culmorum entering into the brewing supply chain can have a major impact on the processability and quality of beer. High F. culmorum infection levels in barley grains result in substantial malt loss, changes in enzymatic activity, kernel ultrastructure deterioration, and DON accumulation. In this study, the protein fractions and protease activity from the resulting infected barley and malt were first characterized. Protein Osborn fractions were extracted and electrophoresed, while the four protease groups were analyzed via specific inhibitors. The results showed significant and relevant differences. Second, in vitro F. culmorum infected malt was used to produce lager beer in a pilot scale facility. The impact of the Fusarium infected malt on a wide range of brewing parameters was measured. It was found that the wort containing infected malt (IW) had a lower pH, higher FAN, higher beta-glucan, and 46% increase in purging rate than the control wort containing uninfected malt (CW). IW caused premature yeast flocculation (PYF), although final extract and attenuation degree were not significantly affected by Fusarium contamination. The final beer quality was fully characterized. The beer produced with infected malt (IB) was compared to the control beer produced with uninfected malt (CB). The IB amino acid profile was considerably different from the CB, while sugar and organic acid profiles were comparable. Flavor characterization of IB revealed a higher concentration of esters, fusel alcohols, fatty acids, ketones, and dimethylsufide (DMS). Acetaldehyde was particularly higher for the IB compared to the CB (98 and 7 mg/L, respectively). Another notable difference for IB compared to the CB was the greater proportion of Strecker aldehydes and Maillard products contributing to an increased beer staling character. Final IB had a 67% darker color with a trend to higher foam stability. The mycotoxin deoxynivalenol (DON) was measured in the malt as well as in the final beer. It was found that 78% of accumulated DON present in the raw material was transferred to the final beer.

Pedro Oliveira studied food science and engineering at the Instituto Superior de Agronomia, Technical University of Lisbon. Pedro was awarded a mobilization scholarship, and for one year he studied at the University College Cork, where he completed his final graduation project on NPD and beverages sciences. During his master’s degree studies , Pedro performed research in the field of beverages and fermented processes focusing on “New Fermented Beverages Using Immobilized Yeast.” Pedro performed an internship in the Manufacturing Support Department at Nestlé PTC, Konolfingen, Switzerland, and gained practical training in the Quality Department at Les Mousquetaires Group on Sensory Analysis. In 2010, Pedro was awarded a postgraduate scholarship by the Irish Research Council for Science, Engineering & Technology and he joined Elke Arendt’s research team at the University College Cork for his Ph.D. Project. His research focus is 1) the impact of infections from Fusarium species on malt quality, with emphasis on mycotoxin production and kernel ultrastructure; and 2) the characterization and identification of antifungal compounds from lactic acid bacteria and their application in malting and brewing. Pedro is a peer support leader and lecturer in the UCC Food Science and Technology course. He is also a member of ASBC and IBD.