Abstract 097
The effect of beer pH on colloidal stabilization with adsorbents
J. Amer. Soc. Brew. Chem. 65 (1): 52-58, 2007
K.J. Siebert and P.Y. Lynn
Solutions of the haze-active (HA) protein gliadin were prepared in buffer at different pHs and treated with silica. Analysis with the bicinchoninic acid and HA protein methods produced similar patterns with greater protein removal near pH 3.5 and pH 5.0. Portions of an unchillproofed beer were adjusted to different pHs, treated with silica and then subjected to HA and foam-active (FA) protein analysis. The HA protein results showed greater protein removal near pH 3.8 and least near pH 4.4. FA protein was little affected although slightly more was removed near pH 4.4. Tannic acid (TA) and catechin were each combined with soluble polyvinylpyrrolidone (PVP) in buffer solutions of different pH; turbidities were determined after incubation. TA formed maximum haze near pH 4, while catechin formed more haze above pH 5. Portions of unchillproofed beer were adjusted in pH and treated with polyvinylpolypyrrolidone (PVPP). The treatment pH had essentially no effect on total polyphenol removal. HA polyphenols were removed to a greater extent near pH 3.8 and near pH 4.6, with lower effectiveness at intermediate pHs. The colloidal stabilization performance of both silica and PVPP was better at pHs near the extremes of the beer pH range. This may account for difficulties in stabilizing some beers.
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