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.
VIEW PRESENTATION 61
