The fate of tannoids during fermentation.

Moll, M., Duteurtre, B., Scion, G., Chapon, L. and Chapon, S.

Abstract
In this study an attempt is made to elucidate the effects of fermentation on the change in the concentration of tannoids. Fermentation is always accompanied by a decrease in tannoids due to (a) adsorption on the yeast cell and (b) decrease in the solubility of some protein-tannin complexes due to the decrease in pH. This decrease is not greatly influenced by the yeast strain, the pitching rate or the fermentation temperature. It is strongly dependent on the nature and tannoid content of the wort. Worts richest in tannoids, which, owing to the general equilibrium between protein and tannin, contain tannoids of higher tanning power than are present in worts low in tannoids, undergo the greatest decreases in tannoids at a given time. Adventitious factors such as oxidation are the cause of such irregularities as are observed in the data presented.
Keywords: beer fermentation polyphenol protein wort