Crystal stability: putting things in perspective
Things have calmed down in the wine cellars. The cold is also penetrating the cellars, causing the substances suspended in the wines to deposit. Real tartar, the potassium salt of tartaric acid, which remains in suspension after fermentation is complete, generally precipitates in cold conditions. Given enough time, the wine usually stabilises on its own. In the case of some wines, though, the time needed is not available. Consumers are already looking forward to the opportunity to buy wines from the 2020 vintage that are ready to drink as soon as possible. Bottling such wines means wine producers have to check crystal stability to prevent any precipitate in the bottle and subsequent complaints. The mini contact process is available, for example, as a potential, highly reliable test procedure. This test analyses the decrease in conductivity over a period of 2-4 hours. The tartar saturation temperature can also be determined in order to reduce the time required.
In case a potential instability is detected, the more accurate test of conductivity can still be considered. Both processes can be carried out using Erbslöh’s EasyKristaTest. There are some influential variables and contexts that should generally be taken into consideration if there are signs of instability. High pH values and alcohol contents, and low temperatures lead to a greater risk of crystallisation, in addition to the tartaric acid, potassium or calcium content. Protective colloids in wine can prevent tartrate precipitation. For this reason there are still a few factors that must be considered before choosing to stabilise the tartar. If deacidification is planned as a wine-making measure shortly before bottling, it should be noted that the use of calcium carbonate can also increase wine’s calcium content. If the wine becomes oversaturated, this leads to production of insoluble calcium tartrate, which cannot be stabilised effectively by adding treatment agents. High temperatures over a period of 6-8 weeks can help to precipitate calcium tartrate. The only option is therefore using Kalinat for a limited de-acidification shortly before bottling. Deacidification has a considerable influence on tartrate stability and should therefore be carried out with great care. The use of cold temperatures, especially when combined with the contact process using Kali-Contact, leads to reliable and prompt precipitation of real tartrate crystals. Planned blending or the addition of unfermented grape juice can also directly affect crystal stability. This can cause a balance that has already been achieved to be disturbed again. The use of stabilising treatment agents is easier and safer.
Optimally esterified Metavin® Opti or even VinoStab® (CMC) are available for instable wines. These products provide effective protection against breakdown of tartar as a result of their colloidal, macromolecular structure. CMC in particular is characterised by its long-term effect. Since December 2019, however, its use has been restricted by law to white and sparkling wines. Products from the Metavin® family are a permitted, reliable alternative for use in red and rosé wines, and for wines produced according to organic principles. The synergistic combination of highly esterified metatartar-ic acid and gum arabic in MetaGum® also leads to long-term crystal stabilisation in wine. There should be no filtration problems if, for metatartaric acid, the recommended reaction time of 3-4 days before bottling is adhered to. Successful wine stabilisation also requires a high level of protein stability, as otherwise the risk of turbidity increases. If proteins have not been previously removed using fining agents, they react with the CMC or metatartaric acid treatment agents to form complexes which cause turbidity. In this case a prior stability check using BentoTEST or a heat test is recommended, in order to predict protein stability. The use of NaCalit® with PORE-TEChnology is recommended as the bentonite treatment needed to thoroughly remove proteins. Stabilisation of the wine requires, as shown, detailed consideration of various factors. A safe product must be ensured using a range of concerted measures if full use cannot be made of the time aspect due to early bottling. Regardless of the bottling deadline, the time for consistent planning of wine-making techniques is a key factor in being able to guarantee successful crystal stability in any case. In summary, it can be stated that premature acceleration of crystal formation on the one hand and prevention of crystal formation on the other are available to prevent crystal precipitation in the bottle. Farsighted winemaking, precise analysis and careful stabilisation processes give the maximum assurance.