PEDRO OLIVEIRA (1), Alex Mauch (1), Fritz Jacob (2), Elke Arendt (1)
(1) School of Food and Nutritional Sciences, National University of
Ireland, University College Cork, Cork, Ireland; (2) Forschungszentrum
Weihenstephan für Brau- und Lebensmittelqualität, Technische Universität
München-Weihenstephan, Freising, Germany
The contamination of barley with Fusarium species has been a
long-standing problem for the malting and brewing industry, causing
significant economical losses. In addition to this, mycotoxins produced
by fungi are a major source of problems with respect to public health.
The objective of this study was to evaluate the impact of Fusarium infection on barley malt quality. Special emphasis was placed on ultrastructural changes, on F. culmorum
growth, as well as the formation of mycotoxins. Malting was carried
using standard MEBAK parameters in a UCC pilot-scale unit. Two different
batches were produced: one control (100% standard barley) and one
contaminated mixture (20% F. culmorum-contaminated-barley + 80%
standard barley). In total, eleven samples for analysis were collected
along the malting process. Raw barley was disinfected by a series of H2O2 baths follow by UV light to be inoculated with an F. culmorum
macroconidia suspension. The fungal growth behavior was evaluated by a
set-up PCR and Fluorometric-based method. After extraction, F. culmorum
was amplified by PCR using primers designed for specific genes involved
in the trichothecene synthesis. The PCR product was then quantified
photometrically by applying a fluorescence dye which specifically binds
to double-stranded DNA. Kernels were analyzed for Fusarium
commonly produced mycotoxins (deoxynivalenol, nivalenol, zearalenone,
and zearalenol) by HPLC. Scanning electron microscope (SEM) and confocal
laser scanning microscope (CLSM) were used to study the kernel’s
ultrastructure. Malt quality was assed by standard methods described by
EBC and ASBC. The contaminated grains exhibit significant fungal growth
during steeping, germination, and kilning. The final barley malt
contained deoxynivalenol at 280 µg/kg. SEM pictures show fungi hyphae
penetrating kernels and destroying the well-structured complexes of
starch granules and protein matrix. Mycelia was able to penetrate
healthy mature kernels from the testa layer, disrupting the aleurone
layer, thus losing its permeability and evidencing extensive amylolysis
and proteolysis degradation. Changes in a kernel’s β-glucan and protein
fractions were clearly seen by CLSM using a series of different dyes. Fusarium contamination also influenced overall malt quality.
Pedro Oliveira studied food science and technology at the Technical
University of Lisbon, Portugal, which included one year at University
College Cork, Ireland. During his master’s thesis studies, “Development
of New Fermented Beverages Using Immobilized Yeast,” he developed
innovative fermentation processes and provided teaching and consulting.
He then joined the Manufacturing Support Department of Nestle in
Switzerland for six months to gain expertise in spray-dryer and
fluidized-bed technology. Next, he joined the Les Mouquetaire Group in
France for eight months to gain expertise in sensory analysis and market
research. He has been a Ph.D. candidate in the School of Food and
Nutritional Sciences, University College Cork (UCC), since 2010. His
main research focus is the application of antifungal compounds from
novel lactic acid bacteria strains isolated from the brewing environment
and their application in malting and brewing. He is also in charge of
UCC microbrewery facilities, and he is giving classes as a demonstrator
in food analysis to students in the Food Science and Technology course.
