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

Abstract

The composition of potassium hydrogen tartrate (KHT) deposits formed on stainless steel surfaces during the cold stabilization of two red wines was determined and compared to those determined in white wines. Polysaccharides and polyphenols were associated with the tartrate crystals. They were present in higher amounts in red wines than in white wines, partly due to the presence of red wine tannins and anthocyanins. Tannins were the major wine components associated with the KHT crystals. Their mean degree of polymerization (DP) was twice the mean DP of wine tannins, which indicated a preferential association of the most hydrophobic molecules with the KHT crystals. Specificities evidenced in white wines with tartrate ester derivatives of phenolic acids and rhamnogalacturonans were confirmed in red wines. Yeast cells represented at least 20% of the tartrate deposits, as compared to 2% in white wines. Observations by scanning electron microscopy suggested that they adhered first on the stainless steel surfaces, where they may act as primary heterogeneous nucleation germs for the KHT crystals. Along with these differences in tartrate compositions, a strong evolution of crystal morphologies was noted between white and red wines.