As a result of climate change consequences, there is a gap between the times at which the grapes reach the phenolic and the technology maturities. As a consequence, the wine sensory properties are affected and, among them, astringency, one of the most important organoleptic attributes for red wine quality. A balanced astringency is essential for quality wines, since when this sensation is perceived with high intensity, it is considered as unpleasant by consumers. The main mechanism described for the astringency development is the interaction of wine phenolic compounds, such as flavanols and flavonols, with salivary proline-rich proteins (PRPs), forming protein-flavanol complexes that can precipitate, resulting in a loss of lubrication in the oral cavity.Although PRPs are the main proteins studied to explain astringency, there are other types of proteins in saliva, such as mucins that are high molecular weight glycoproteins representing the main proteins in the salivary proteome. It has been reported that mucins can interact with wine flavanols, which could compromise the lubricating functions of mucins, so these proteins may play an important role in astringency sensation.1 Thus, it is important to go deeper into the study of the interactions of these proteins with wine phenolic compounds and the factors that could affect them to get new insight about the mechanisms of astringency sensation.Flavanols and flavonols are also involved in the stabilization of colored forms of malvidin-3-O-glucoside (Mv) through copigmentation effect. Moreover, it has been reported that some flavanol-anthocyanin mixtures present a synergic effect toward the interaction with PRPs when compared to individual polyphenols.2 Hence, the main aim of this work is to assess if the interaction between flavanols and flavonols and high molecular weight proteins is affected due to the involvement of these phenolic compounds in the copigmentation effect. To do this, ternary interactions involving Mv, two individual flavanols (catechin and epicatechin) and/or the flavonol quercetin-3-O-glucoside with mucin from bovine submaxillary glands have been studied by isothermal titration calorimetry (ITC).ITC results show that the studied interactions are driven by both hydrophobic interactions and H-bonds. Results show that mucin interact with the wine phenolic compounds assayed, confirming the possible role of mucins in astringency sensation due to the effect that this interaction may have on lubricating functions of these proteins. Moreover, the presence of anthocyanins in the mixtures affects the interaction between mucins and the phenolic compounds studied, which points out that anthocyanins could play an indirect role on astringency development ant that the whole wine phenolic composition should be considered when astringency sensation is studied.
Authors: Torres-Rochera Bárbara1, García-Estévez Ignacio1 and Esribano-Bailón Mará Teresa1
1Department of Analytical Chemistry, Nutrition and Food Sciences, Universidad de Salamanca
*corresponding author: barbara.torres@usal.es
References:
(1) Brandão, E. et al. Molecular study of mucin-procyanidin interaction by fluorescence quenching and saturation transfer difference (STD)-NMR. Food Chem. 2017, 228, 427-434.
(2) Soares, S. et al. Effect of malvidin-3-glucoside and epicatechin interaction on Ttheir ability to interact with salivary proline-rich proteins. Food Chem. 2019, 276, 33–42.
Keywords: astringency, copigmentation, wine phenolic compounds and ITC
