Abstract 090
Comparison of methods for measuring protein in beer
J. Amer. Soc. Brew. Chem. 63 (4): 163-170, 2005
K.J. Siebert and P.Y. Lynn
Mixtures containing various combinations of haze-active (HA) and non-HA proteins (water soluble hordein and lysozyme, respectively) and HA and non-HA polyphenols (tannic acid and epicatechin) were prepared in buffer model systems. A battery of protein methods (the Bradford Coomassie blue dye binding method (CBB), HA (sensitive) protein, the Bicinchoninic acid (BCA) method, and 280 nm absorbance) were applied to each sample and the results were compared. The various methods gave quite different responses to the different test compounds. With concentrations of the various substances roughly equivalent to those found in beer, 280 nm absorbance and BCA suffered strong interference from the polyphenols. The CBB and HA protein methods, on the other hand, responded very little to polyphenols. CBB response was much greater to lysozyme than to hordein. TA haze induction responded only to HA protein, but exhibited some non-linearity. Results obtained when these methods are applied to beer must be interpreted with caution.
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