Interactions of enological tannins with the protein fraction of saliva and astringency perception are affected by pH

Abstract

The effects of pH on both tannin-induced astringency and tanninesalivary protein interactions were investigated. A trained sensory panel evaluated astringency perception. Tanninesalivary protein interactions were assessed in vitro by examining the effects of either a condensed enological tannin or an hydrolyzable enological tannin on two physicochemical properties of the protein fraction of saliva, namely, its mode of diffusion on cellulose membranes and its precipitation. Comparative assays mimicking the degree of dilution experienced by saliva during a tasting assay were performed at pH 3.5 and pH 7.0. Results indicated that both enological tannins were perceived as clearly more astringent at pH 3.5 compared with pH 7.0. In addition, the effects of tannins on protein diffusion and protein precipitation were markedly exacerbated at pH 3.5.