Effect of beta-glucan and environmental factors on the physical and chemical properties of wort and beer

Behaviour of barley β-(1 → 3)(1 → 4)-D-glucans in wort and beer was examined to investigate their effect on brewing process and beer quality. Beta-glucans at 0–1000 mg/L increased wort and beer viscosity linearly with MW and concentration. The Arrhenius relationship governed the effect of temperature on wort viscosity. Beta-glucan viscosity in wort was lowered after shearing although shearing increased the apparent wort viscosity (p < 0.001). Shearing decreased beer viscosity (p < 0.001) but did not affect the β-glucan viscosity in beer (p > 0.05). Shearing temperature did not affect the viscosities of wort or beer (p > 0.05). Increasing pH raised wort viscosity (p < 0.001) but did not affect beer viscosity (p > 0.05). Maltose in wort and ethanol in beer enhanced the viscosity of β-glucan polymers (p < 0.001). Beta-glucan-caused viscosity was found to be an indicator of potential technical problems. Beta-glucans had higher intrinsic viscosities (5°C) in beer than in wort (p < 0.001). The critical overlap concentration (C*) for β-glucans (31–443 kDa) in beer and wort was found to vary in the range of 1.3–8.3 g/L.; Apparent particle size of β-glucans in wort and beer increased with their MW and concentration (p < 0.001). Beta-glucans had greater particle size in beer (mainly 0.01–0.1 μm in diameter) than in wort (even distributed in <0.01 μm and >0.01 μm fractions) (p < 0.001). Beta-glucan particles were larger at higher pHs of wort and beer (p < 0.001). Maltose did not affect the β-glucan particle size distributions in wort (p > 0.05). High ethanol concentrations increased the 0.01–0.1 μm fraction and decreased the >0.1 μm fraction of the 443 kDa β-glucan in beer (p < 0.001). Shearing of wort and beer resulted in a decrease in the <0.01 μm fraction of β-glucans and an increase in 0.01–0.1 μm β-glucan fraction (p < 0.001) but shearing temperature did not affect the particle size distribution (p > 0.05).; Wort and beer turbidity increased with higher MWs and concentrations of β-glucans (p < 0.001), shearing (p < 0.001), lower maltose and ethanol levels and lower pHs (p < 0.001). Shearing (20–76°C) at high temperatures resulted in lower wort turbidity values than low temperatures (p < 0.001) but shearing temperature (0–10°C) did not affect beer turbidity (p > 0.05). (Abstract shortened by UMI.)...