TARTRATE STABILITATION IN WINE MAKING
Tartrates are also known as wine argols. Is the generic term applied to the crystalline deposits that spontaneously precipitate during fermentation or ageing of wines. This is a consequence of the insolubility of the salts of tartaric acid in alcoholic solutions at low temperatures. The most abundant is potassium acid tartrate or cream of tartar, though calcium tartrate may also precipitate as parts of sediment.
Their presence in quality wines is increasingly accepted because it simply indicates fewer manipulations in the making process (i.e. minimal cold stabilization, non-aggressive filtration, etc.) and, moreover, they carry many beneficial compounds for human health as are polyphenols and tannins. Nevertheless, many consumers do not appreciate their presence in every day wines, considering them as clouds.
The process by which they are removed is called tartaric stabilization (cold stabilization, by means of resins, mannoproteins, electrodialysis, etc). Stabilization, is a set of fundamental winemaking operations which principally aim at ensuring quality and stability of the wine before it reaches the market, as well as allowing it to develop correctly inside the packaging as it moves along the distribution chain and during laying down or storing. These operations complement and mingle with those of clarification, though more specifically intended to assure microbiological and physical-chemical stability (thus avoiding faults casses).
Microbiological stability is achieved by averting the growth of undesirable yeasts and bacteria, which may lead to fermentation in bottle or to wines becoming pricked. For this reason, controls over levels of residual sugar, total acidity and aeration are essential. Careful employment of sterilization techniques (i.e. pasteurization) during filtration and bottling, as well as correct usage of sulphur dioxide or the adequate realization of malolactic fermentation (e.g. through controlled addition of lysozyme) would suffice in this case.
As for physical-chemical stabilization, there are many ways to achieve it, of which some of the most outstanding are cold stabilization and filtration, electrodialysis, use of metatartaric acid, oenological tannins, calcium tartrate, resins, mannoproteins (tartaric stabilization), selective fining for eliminating unwanted polymers as proteins and tannins, or corrective measures for ferric or copper-caused wine faults.
