Red Wine Tannins Fluidify and Precipitate Lipid Liposomes and Bicelles. A Role for Lipids in Wine Tasting? Aure ́ lien L. Furlan, † Aurore Castets, † Fre ́ de ́ ric Nallet, ‡ Isabelle Pianet, § Axelle Gre ́ lard, † Erick J. Dufourc, † and Julie Ge ́ an* ,† † Institute of Chemistry and Biology of Membranes and Nano-objects, UMR 5248, CNRS, University of Bordeaux, IPB, F-33600 Pessac, France ‡ CRPP, UPR 8641, CNRS, University of Bordeaux, F-33600 Pessac, France § ISM, UMR 5255, CNRS, University of Bordeaux, IPB, F-33400 Talence, France * S Supporting Information ABSTRACT: Sensory properties of red wine tannins are bound to complex interactions between saliva proteins, membranes taste receptors of the oral cavity, and lipids or proteins from the human diet. Whereas astringency has been widely studied in terms of tannin-saliva protein colloidal complexes, little is known about interactions between tannins and lipids and their implications in the taste of wine. This study deals with tannin-lipid interactions, by mimicking both oral cavity membranes by micrometric size liposomes and lipid droplets in food by nanometric isotropic bicelles. Deuterium and phosphorus solid-state NMR demonstrated the membrane hydrophobic core disordering promoted by catechin (C), epicatechin (EC), and epigallocatechin gallate (EGCG), the latter appearing more efficient. C and EGCG destabilize isotropic bicelles and convert them into an inverted hexagonal phase. Tannins are shown to be located at the membrane interface and stabilize the lamellar phases. These newly found properties point out the importance of lipids in the complex interactions that happen in the mouth during organoleptic feeling when ingesting tannins. ■ INTRODUCTION Condensed tannins or proanthocyanidins are the most abundant polyphenols in red wines. They are derived from the polymerization of flavan-3-ol units such as catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). Condensed tannins from grape seeds and skins are known to play an important gustative role since they contribute to red wine astringency, a dry and rough sensation in the mouth during red wine tasting. This feeling results from the formation of precipitating colloidal complexes between tannins and pro- line-rich salivary proteins. 1-6 Moreover, tannins are also known to interact with lipid bilayers, 7-9 an association that is very likely to influence wine tasting. Lipid polymorphism is very important (lamellar phases, multilamellar liposomes, micelles, cubic, sponge or hexagonal phases, bicelles, monolayers, etc.), and two main lipid organizations may be thought to play key roles in modulating the interaction: lipids as membrane components of the oral cavity and/or lipids as colloidal components in fatty foods. The influence of food on the sensory perception of wine is well-known from the oenological viewpoint, but little is known from a molecular viewpoint. Notably, it is interesting to describe and analyze the effects of tannins on lipids in the frame of wine tasting. Physicochemical studies suggest that the affinity of catechins for the lipid membrane may be governed by the catechin chemical structure and also by the electric charge of the lipid membrane or of the medium. 8,10,11 Association of catechins to lipid membranes is suggested to depend on their octanol-water partition coefficients, K ow . Measured values for C, EC, EGC, ECG, and EGCG are respectively 2.4, 2.4, 0.3, 48.0, and 12.1 12 and are consistent with a thermodynamically favorable interaction with the membrane. 10,13-16 The effects of catechins on the membrane structure and organization are still subject to debate. Galloylated catechins (ECG, EGCG) show a sealing effect at very low concentration (below 1 nM) on Egg PC SUV, 8 whereas they promote leakage at micromolar concen- trations on LUV composed of a mixture of Egg PC and PG, a negatively charged phospholipid. 13 On the other hand, controversial effects of catechins on membrane fluidity have been reported. Tsuchiya et al. have concluded from polarization Received: February 6, 2014 Revised: April 18, 2014 Published: May 2, 2014 Article pubs.acs.org/Langmuir © 2014 American Chemical Society 5518 dx.doi.org/10.1021/la5005006 | Langmuir 2014, 30, 5518-5526