Composition of Tartrate Precipitates Deposited on Stainless Steel Tanks During the Cold Stabilization of Wines. Part I. White Wines

摘要

The crystallization of tartrate salts, mainly potassium hydrogen tartrate (KHT), is a major instability in wines. KHT solubility is largely dependent on the wine composition. Though the incidence of wine components is not fully understood, it is recognized that some of them may inhibit the KHT crystallization by adsorption on the crystal growth faces. The identification of the organic components which precipitate out with KHT is a potential approach to identify crystallization inhibitors. Moreover, it can improve the understanding of the KHT behavior in wine. The present study deals with the identification of organic compounds associated to KHT crystals obtained from the cold stabilization of two white wines. Tartrate esters of phenolic acids and polysaccharides accounted for 0.2/100 to 0.8/100 of the crystal dry weight. Among phenolic acids, a specific affinity of 2-S- glutathionylcattaric toward the KHT crystal surfaces was observed and attributed to its glutathionyl moiety. Polysaccharide distribution in KHT crystals differed largely from that of the starting wines. Rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II) had a peculiar behavior. RG-I adsorbed preferentially on the crystal surfaces, whereas RG-II was not detected. Arabinogalactans and mannoproteins were also associated with tartrate crystals, and may thus impede crystal growth. Yeast cells accounted for 2/100 of the dry matter and may act as heterogeneous nucleation germs.