Effect of flavonols on wine astringency and their interaction with human saliva

• Flavonol addition to wines yields in an increase in the astringency and bitterness.
• Flavonols interact with salivary proteins forming complexes.
• Flavonol-protein complexes were monitored by molecular dynamics simulations.
• Flavonol-protein quenching constants were determined.

The addition of external phenolic compounds to wines in order to improve their sensory quality is an established winemaking practice. This study was aimed at evaluating the effect of the addition of quercetin 3-O-glucoside on the astringency and bitterness of wines. Sensory results showed that the addition of this flavonol to wines results in an increase in astringency and bitterness.Additionally, flavonol-human salivary protein interactions were studied using fluorescence spectroscopy, dynamic light scattering and molecular dynamic simulations (MD).The apparent Stern-Volmer (KsvApp) and the apparent bimolecular quenching constants (kqApp) were calculated from fluorescence spectra. The KsvApp was 12620 ± 390 M−1, and the apparent biomolecular constant was 3.94 × 1012 M−1 s−1, which suggests that a complex was formed between the human salivary proteins and quercetin 3-O-glucoside.MD simulations showed that the quercetin 3-O-glucoside molecules have the ability to bind to the IB937 model peptide.