Comparison of methods for measuring polyphenols in beer

Mixtures containing various combinations of haze-active (HA) and non-HA polyphenols (tannic acid and epicatechin, respectively) and HA and non-HA proteins (water soluble hordein and lysozyme, respectively) were prepared in buffer model systems. A battery of polyphenol methods (the Folin-Ciocalteu method, the international method for total polyphenols in beer, and the HA polyphenol method) were applied to each sample and the results were compared. The various methods gave quite different responses to the different test compounds. The best measure of the polyphenols involved in astringency and haze formation was obtained with an improved HA polyphenol method. Results of this method are, however, likely to be affected by endogenous HA protein.