Effects of β-Glucans and Environmental Factors on the Viscosities of Wort and Beer
Yu-Lai Jin 1, Alex Speers 1, 3, Allan T. Paulson 1, and Robert J. Stewart 2
1 Department of Food Science and Technology, Dalhousie University,
1360 Barrington Street, D401, Halifax, NS, Canada B3J 2X4.
2 Labatt-ITW Technology Department Americas, 197 Richmond
Street, London, ON, Canada N6A 4M3.
3 Corresponding author. E-mail: Alex.Speers@Dal.Ca
J. Inst. Brew. 110(2), 104-116, 2004 | VIEW ARTICLE
ABSTRACT
This paper reports on the influence of molecular weight and concentration
of barley β-glucans on the rheological properties of
wort and beer. Environmental conditions such as pH, maltose
level in wort, ethanol content of beer, shearing and shearing
temperature were also examined for their effects on wort and
beer viscosities. In the range of 50-1000 mg/L, β-glucans increased
solution viscosity linearly with both molecular weights
(MW) of 31, 137, 250, 327, and 443 kDa and concentration. The
influence of MW on the intrinsic viscosity of β-glucans followed
the Mark-Houwink relationship. Shearing wort and beer
at approximately 13,000 s -1 for 35 s was found to increase the
wort viscosity but reduce beer viscosity. Shearing wort at 20°C
influenced β-glucan viscosity more than shearing at 48°C and
76°C whereas the shearing temperature (0, 5 and 10°C) did not
effect the viscosity of beer. At lower pHs, shearing was found to
reduce the viscosity caused by β-glucans in wort but had no
effect in beer. Higher concentrations of maltose in wort and
ethanol in beer also increased the viscosity of β-glucan polymers.
It was found that β-glucans had higher intrinsic viscosities
in beer than in wort (5°C), and lower critical overlap concentrations
(C*) in beer than in wort.
Key words:
Beer, beta-glucan, ethanol, maltose, shear, viscosity,
wort.
Publication no. J. Inst. Brew. G-2004-0524-220 ©2004 The Institute & Guild of Brewing