WINETECH Technical Yearbook 2021

PRACTICAL IN THE CELLAR | NOVEMBER 2021

The cold stabilisation tests of wine

CHARL THERON: Private consultant KEYWORDS: Cold stabilisation, tartrate stability.

THE COLOUR, FLAVOUR AND TASTE STABILITY of wine is a basic requirement of most wine consumers. Different wine making procedures are applied to obtain it. In order to determine the efficiency of the stabilisation procedures certain tests are applied. Tartaric acid is less soluble in alcoholic aqueous solutions at lower temperatures and the adding of different compounds can influence the precipitation. In an over-saturated solution, the different tartrate ions do not align in such a way that crystal formation and precipitation occur permanent ly. Over t ime the precipitation of crystals will however occur. Lower temperatures decrease the distance between the ions and even small dust particles can serve as nucleus for crystallisation. Different stabilisation tests were developed over time to evaluate and

ensure the cold stability of wine. These tests can be analytical or cellar procedures. The so-called cold test is actually only an imitation of the original tartrate stabili- sation procedure where wine is kept at a low temperature for a certain time. The temperature decrease causes a lowering in the solubility of the tartrates. The process is however time consuming and commer- cially much tank space and cooling energy are required. It does also not cause or test absolute tartrate stability, because the tem- perature after cooling is actually the stabili- ty limit. This method can be accelerated by the addition of potassium bitartrate as seed crystals, because the addition will increase the oversaturation. The freeze and thaw test is done by freezing the wine for approximately 12 hours after filtration. After thawing of the wine a few crystals will be visible. After another hour

Cold stability of wine can be determined analytically. (Photo: Vinlab).

WINETECH TECHNICAL YEARBOOK 2021 | 168