Scientists are working on ways of influencing the ageing of wine by controlling the behaviour of tannins.
Scientific studies into the complex subject of wine maturation usually centre on chemistry, but a new study is focusing on the physics of the way tannins behave. Tannins are one of the major factors determining ageing potential in red wine.
Professor Dražen Zanchi of the Laboratoire de Physique Théorique et Hautes Energies in Paris is looking into the colloid structure of tannins and the way they ‘polymerise’ (stick together). By controlling the rate at which they polymerise, Zanchi reckons he can speed up or slow down the ageing process.
‘It is one of the biggest questions of modern enology to know how the astringency and ageing potential (of a wine) are related to the colloid structure,’ Zanchi says in his research proposal.
‘Colloid structure’ refers to the way the tannin molecules are assembled. A colloid is a mixture of minute particles of one substance suspended in another substance in which it does not dissolve – in this instance, tannins in wine. Tannins consist of collections of chains of smaller units. The way they are made up has an impact on the ageing potential of the wine, and the tannic ‘mouthfeel’ of the wine.
Tannin molecules stick together to form larger molecules (colloids) in the wine. Although the initial polymerisation process is a chemical action, this ‘sticking together’ relies on physical forces and interactions. The units themselves vary in size and the molecules they form can differ considerably in length and configuration, being irregular or compact, rough or smooth, and so on.
As polymerisation goes on in the barrel and bottle, the particles become too heavy to be held in solution and precipitate to the bottom, in the form of sediment, leaving the wine less astringent and less ‘tannic’.
Zanchi believes that by ‘controlling colloidal structure one could expect to be able to control the (further) polymerisation’, so influencing the way tannins feel in the mouth and the wine’s potential for maturation.
This project, currently in its preliminary phase, will be conducted in collaboration with several other leading experimental physicists, including Aude Vernhet and Celine Poncet-Legrand from the enology group at the University of Montpellier.
Written by Penny Boothman