Glen Fox (1), Evan Evans (2); (1) University of Queensland, Brisbane, Australia; (2) The Tassie Beer Dr., Lindisfarne, Australia
Technical Session 7: Brew House Operations
Monday, August 15 • 8:15–9:30 a.m.
Tower Building, Second Level, Grand Ballroom
A key biochemical process in brewing is the hydrolysis of starch by
DP enzymes into yeast-fermentable sugars during the mashing stage of
brewing. Efficient starch hydrolysis during mashing requires starch
gelatinization at ~62-64°C, along with sufficient DP enzyme activity to
achieve starch hydrolysis. This investigation considers the release of
yeast-fermentable sugars in parallel with the activity of the DP enzymes
during a modified IoB 65°C (1:3 grist/water + Ca), with a conventional
Congress (1:4 grist/water) small-scale mash, using malt from three
current Australian varieties. Traditionally, it is recognized with the
DP enzymes that alpha-amylase is relatively thermostable while
beta-amylase and limit dextrinase are relatively thermolabile at
conventional mashing temperatures. In addition, it is know that
beta-amylase, and in particular limit dextrinase, have bound and latent
fractions that require release from inhibitors or binding proteins
before they are able to contribute to starch hydrolysis. One empirical
mechanism appears to be that the heat applied during mashing at
temperatures around 55-60°C liberates these enzymes. Of similar
importance is the structure of starch, which determines the temperature
of gelatinization. In addition, starch branching and chain length are
important to the efficiency of hydrolysis by the DP enzymes. The results
in terms of starch characteristics, DP enzyme release, thermostability
and activity is examined to understand the relative contribution of the
DP enzymes to fermentable sugar production in the mash. Interestingly,
both beta-amylase and limit dextrinase were observed to retain
significant levels of activity (~40% total activity), even after mashing
for 60 min at 65°C. These observations are of critical importance to
brewers when they manipulate mash temperatures to cope with variations
in malt quality or to develop new products. It is well understood that a
mash temperature between 60 and 70°C and beyond has a substantial
impact on the level and composition of wort lipids, free amino nitrogen
and fermentable sugars. The level and composition of all these wort
components are known to effect yeast metabolism and subsequently beer
flavor. Finally, these understandings also have significant implications
for the choice of small-scale mash protocol for malt quality
evaluation, the targeting of DP enzyme alleles for barley malt quality
improvement and the selection of malt for brewing.
Glen Fox joined the University of Queensland’s Centre for
Nutrition and Food Science in October 2010, after 25 years of conducting
research projects with the Queensland government. He obtained his Ph.D.
degree from Southern Cross University in the area of barley genetics
related to barley and malt quality. In 2008-2009, he was a postdoctoral
fellow at the Department of Food Science, Stellenbosch University, South
Africa, and appointed adjunct professor in 2012. In 2013, he was
appointed to the College of Experts for the Global Change Institute at
the University of Queensland. He has a vast amount of knowledge in
value-adding of cereals, particularly barley, malt and beer quality,
including starch structure and fermentability. He has collaborated with
major global brewing companies and partnered in all the Australian
states, the United States, Canada, South Africa, China, Ethiopia, Kenya
and the United Kingdom. Glen also has research activities on maize and
sorghum covering food security in several African countries. Glen is on a
number of national and international technical committees, including
the Institute of Brewing & Distilling Asia Pacific Section
Analytical Methods Sub-committee and the European Brewery Convention
Brewing Science Group.
