E. EVANS (1), M. Kaur (2), J. Bowman (2), A. Janusz (3), D. Stewart
(3), A. Koutoulis (2); (1) AEGIC, Hobart, Australia; (2) University of
Tasmania, Hobart, Australia; (3) Joe White Maltings, Adelaide, Australia
Malt
Wednesday, June 4 - 3:00 p.m.-4:45 p.m.
Level 4, Red Lacquer Ballroom
PYF is an intermittent issue in the brewing industry that results in
incomplete yeast utilization of fermentable sugars in the wort,
resulting in out-of-specification beer and disrupted brewing production
schedules. Its occurrence leads to significant economic losses for the
affected brewer. Previous investigations have determined that PYF is
associated with certain batches of malt and due to unfavorable but
ill-defined interactions with barley microbes during malting.
Consequently, the brewing industry relies on small-scale fermentation
assays that are broadly expensive, time-consuming, and inconsistent. To
identify the putative causal microbes, tag-encoded pyrosequencing of the
conserved fungal large subunit rRNA LSU and ITS regions was applied for
the first time to comprehensively assess the fungal population
diversity of 32 different malts whose PYF status had been determined by a
variety of fermentation tests (15 PYF+ve and 17 PYF–ve). On average
20,000 sequences were obtained for each sample. Bioinformatic and
statistical analyses were applied to identify the likely PYF causal
genera from these samples. From this analysis and review of the
literature 19 fungal taxa were selected to design 25 unique primer and
probe pairs for qPCR analysis. After optimizing the qPCR conditions, 85
malt samples (including the 32 samples sequenced) were analyzed by qPCR
using 15 specific primers and probes. The rRNA gene copy numbers of the
specific taxa were calculated for each malt sample. Based on statistical
analysis, the PYF designation was highly significant (P <
0.0034). Further assessment of the qPCR data suggested that the 4
genera/6 primers that identified them were of most practical value in
determining the PYF status of malt samples. The selection of these
primers is currently being refined and validated with interested
brewers. It is hoped that this research will result in a timely,
reproducible, and cost-efficient test for routine malt PYF status
determination. Ultimately, it is hoped that the causal microbe(s) and
flocculating factor(s) will be unambiguously identified and the malting
conditions that favor them will be defined.
Evan Evans graduated with a B.Agr.Sc. (honors) in 1986, followed by a
Ph.D. Degree in 1990, both from the University of Melbourne. In 1992,
he joined the University of Adelaide, where he developed his interest in
malting barley and brewing. Between 2002 and 2013 he relocated to the
University of Tasmania, working toward improving malt quality to improve
beer quality and the efficiency of the brewing process. In 2013, Evan
joined the Australian Export Grains Innovation Centre and continues to
work on malt quality. He is currently serving on the IBD Awards
Committee and is a member of the editorial board for the ASBC Journal.
In 2005, Evan was named a Fellow of the Institute of Brewing and
Distilling. In 2009, he was an inaugural debater for the ASBC Pearls of
Wisdom session on beer foam quality.
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