An increase in calcium precipitation in wines

Unlike potassium bitartrate, which has transparent crystals, neutral calcium tartrate has a whitish appearance in white and rosé wines. In red wines, it resembles tartar crystals but the deposit is lighter," said Laeticia Etourneau, head of microbiology at the Excell laboratory, in her introduction to a webinar on 18 March on turbidity and deposits in wines. The white deposit stems from the reaction between calcium, naturally occurring in wine, and tartaric acid. Like potassium bitartrate or any other deposit in the bottle, cloudiness is not appreciated by consumers and should be avoided at all costs.

“Calcium is absorbed by vines when they undergo stress”, explained Lola Goulevant, Lamothe Abiet's product manager for the maturation range, in another webinar on the same topic. Hot vintages in recent years have therefore promoted an increase in calcium concentration in wines. “Also, it is important to know that the higher the pH, the more unstable the calcium. This is why we are seeing an increase in calcium precipitation”.

“There is no specific measurement of calcium stability, unlike tartaric stability, which is assessed with the cold test”, continued Etourneau. To assess the risk of precipitation, calcium must be measured in the wines. “We consider that there is a risk if the concentration is higher than 60 mg/L in reds and 80 mg/L in whites and rosés. Often, tartaric precipitation causes calcium precipitation, but this is not systematic. The cause of calcium precipitation alone, if it does occur, is therefore not yet well known”.

Lamothe Abiet believes that stabilisation methods are the same in both cases: “refrigeration, electro dialysis, adding metatartaric acid, CMC or yeast mannoproteins”, said Goulevant. If cloudiness has already formed in the bottle, Etourneau recommends measuring the remaining calcium in the wine to find out if the deposit is likely to continue, “as this is the case when there is at least 30 mg/L of calcium left in the wine”.