Malt and Grains Session
Shang Chu, The University of Queensland, Brisbane, Queensland, Australia
Co-author(s): Jovin Hasjim, University of Queensland, Brisbane,
Australia; Kevin Redd and Evan Evans, University of Tasmania, Hobart,
Australia; Glen Fox, University of Queensland, Brisbane, Australia;
Robert Gilbert, University of Queensland, Brisbane, A
ABSTRACT: During the barley mashing process, starch
molecules are hydrolyzed to smaller sugars and dextrin by degrading
enzymes (either naturally occurring in the malt or commercial exogenous
enzymes). It is well known that the sugar profile of wort plays an
important role in the fermentation process. There are several
controlling factors in the production of fermentable sugars during
mashing. Starch structure may well be one of these factors, as different
starch structural features lead to different enzymatic degradation
rates, and thus affect the fermentability of wort. In order to study the
role of starch structure in the production of fermentable sugars in
wort, 10 different varieties of both barley malts and un-malted barley
grains were used to undergo the mashing step. A number of commercial
exogenous enzymes were added for un-malted samples. Twenty portions of
wort were then collected for sugar profile analysis using
high-performance liquid chromatography. To characterize starch
structure, the branched and debranched size distributions of starch
molecules from the 20 barley malts and grains were obtained using
size-exclusion chromatography. Detailed chain length distributions of
the samples were obtained through fluorophore-assisted carbohydrate
electrophoresis. The structural characteristics of starch crystalline in
the samples were described using small and wide angle X-ray scattering.
Logistic regression was applied to analyze the relationship between
barley starch structure and fermentability of wort. The results
indicated a significant correlation between structural characteristics
of barley starch and the sugar profile of wort. By increasing the
understanding of the role of starch structure in beer brewing, we can
provide brewers and breeders with improved methods to select more
suitable barley for the beer they wish to produce.
Shang Chu
received a B.S. degree in biology and a B.Eng. degree in water resources
from Wuhan University in Wuhan, China. He then received an M.S. degree
in biotechnology from the University of Queensland, Brisbane, Australia.
He is currently enrolled in his Ph.D. program under the supervision of
Robert G. Gilbert since 2010 in the Centre for Nutrition and Food
Sciences, Queensland Alliance for Agriculture and Food Innovation, the
University of Queensland. He is a member of the Nutrition Society of
Australia.
