Résumé
The influence of wine polymers on the spontaneous precipitation of calcium tartrate in a model wine system has been examined. Rhamnogalacturonan-I was identified as the most effective inhibitor (precipitation induction time of 180min compared with 7min for the standard model). It is argued that this is a consequence of rhamnogalacturonan-I's ability to participate in the egg-box' type sequestration of calcium ions. The more structurally complex rhamnogalacturonan-II had only a minor influence on the induction time (22min). Arabinogalactan proteins and mannoproteins also have little influence with induction times ranging from 12 to 15min. An ultra-filtration study of four Chardonnay wines, prepared with and without the use of pectolytic enzymes, was performed in a search for conditions that might maximise the concentration of rhamnogalacturonan-I. However, rhamnogalacturonan-I could not be identified in any of the four wines. Implications of these observations, specifically the need to understand the inhibition exerted by specific uronic acids, for winemaking and calcium tartrate precipitation are discussed.