Tannin–protein interaction is more closely associated with astringency than tannin–protein precipitation: experience with two oenological tannins and a gelatin

Abstract

SummaryRelative abilities of two commercial oenological tannins to interact with a single oenological gelatin were compared with their relative abilities to elicit astringency. A trained sensory panel assessed astringency, whereas the interaction between tannins and gelatin was estimated by observing the ability of tannins both to interfere with gelatin diffusion on a cellulose membrane and to form tannin–gelatin precipitates. HPLC‐DAD chromatography and spectroscopic analysis showed that one of the commercial tannins was a hydrolysable tannin, while the other one was a condensed. The majority of the sensory panelists recognised the hydrolysable tannin as far more astringent than the condensed. The more astringent oenological tannin was found to interfere markedly with gelatin diffusion on a cellulose membrane, but it failed to produce tannin–gelatin precipitation. The condensed oenological tannin both interfered with gelatin diffusion and was a powerful gelatin‐precipitant. This study supports the hypothesis that astringency correlates better with tannin–gelatin interaction than tannin–gelatin precipitation.