Update knowledge about the presence of condensed tannins in grapes and their contributions to astringency perception
Abstract
Condensed tannin is a principle group of polyphenol compounds derived from grape, greatly contributing to the bioactivity and the sensory perception of wine. Condensed tannins present as a heterogeneous mixture in nature involving various degrees of both polymerization and galloylation. Even though multiple attempts focusing on fractionation of grape condensed tannins by solid-phase have been conducted over the past decades, few individual tannins have been purified and identified. Hence, our knowledge on grape and wine condensed tannin moleculars has to be limited at the several known monomeric, dimeric and trimeric proanthocyanidins. In the present study, a rapid and effective approach was developed to isolate the galloylated proanthocyanidin from the non-galloylated forms in grape seed tannins and fractionate the non-galloylated proanthocyanidin according to their degree of polymerization by the technique of Centrifugal partition chromatography (CPC). The application of CPC on grape tannins fractionation is efficient, less-time consuming, less expensive and with higher recovery. More importantly, it could effectively isolate galloylated tannins at the beginning and eliminate its interference in the other fractions. After fractionation performed by the technique of CPC, the repurification was achieved by either preparative hydrophilic interaction chromatography or reversed phase high-performance liquid chromatography (HPLC). Eventually, a series of individual condensed tannins with certain degree of polymerization and galloylation from grape were isolated successively. Analyte identity and purity were examined by reversed-phase UPLC-DAD-ESI-Q-TOF and normal-phase HPLC-UV-Fluo-MS, respectively. The astringency perception contributions of the purified individual tannins were examined by the approach of salivary binding ability test. The results were observed by HPLC-Fluo and quantified by the difference of the amount of proanthocyanidins between before and after interaction.
Issue: Macrowine 2016
Type: Poster
Authors
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