Effects of β-Glucans and Environmental Factors on the Viscosities of Wort and Beer

Abstract

This paper reports on the influence of molecular weight and concentration of barley ␤-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, ␤-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 ␤-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 ␤-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 ␤-glucans in wort but had no effect in beer. Higher concentrations of maltose in wort and ethanol in beer also increased the viscosity of ␤-glucan polymers. It was found that ␤-glucans had higher intrinsic viscosities in beer than in wort (5°C), and lower critical overlap concentrations (C*) in beer than in wort.

Optimisation of a Mashing Program for 100% Malted Buckwheat

“…High apparent viscosities can lead to problems in lautering and beer filtration 23 . In worts derived from barley malt, high viscosities are usually caused by 1,3-1,4 ␤-glucans.…”

Effects of β-Glucan, Shearing and Environmental Factors on the Turbidity of Wort and Beer

“…The increased turbidity by shearing was previously explained by an increase in ␤-glucan particle size after shearing 12 . This result confirmed previous reports from this laboratory that noted ␤-glucan turbidity increases after shearing 12,18,19 .…”

“…The increase in turbidity was proportional to the increase in MW and concentration (R 2 -adj = 0.851; n = 80; p < 0.001). Beta-glucan complexes of higher apparent MW and concentration have larger apparent sizes 8,12 , which scatter more light at 90°. However, wort samples were all brilliant since the turbidity values were lower than 35 FTU (Fig.…”

“…Particles below 0.1 µm scatter substantial light 90° to the incident beam and result in so-called "pseudo-" or "invisible" hazes 2,3,11,15,26 . When added to beer, ␤-glucans having molecular weights (MWs) of 31-443 kDa are primarily 0.01-0.1 µm in apparent diameter 12 . The purpose of this study was to investigate how ␤-glucan MWs and concentrations affect the turbidity of wort and beer.…”

“…This wort was further treated with a commercial ␤-glucanase (Filtrase B TM , containing at least 180 U/g with maltodextrin as carrier, DSM Food Specialties, Seclin, FRA) to reduce its ␤-glucan to an undetectable level by Congo red assay 12 . This ␤-glucan-free wort was dispersed into 1 L Erlenmeyer flasks and covered with 4 layers of aluminum foil.…”