The relationship between barley starch structure and the sugar profile of wort

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.