Ullage

Ullage refers to the amount of airspace in any container holding wine. This applies to tanks, barrels, amphora or anything else wine is held in during the making of the wine and to wine bottles. Depending on the style being made ullage may be avoided or encouraged. In the case of Sherry, Vin Jaune or Madeira, ullage is an essential part of developing these wines unique characters. Taking Sherry as an example, the oxygen in the ullage space interacts with the flor floating on top of the wine, nourishing it and resulting in the aromas and flavours unique to Sherry.

For table wines styles where extremely oxidative techniques aren’t being used ullage is avoided to stop the wine going volatile and becoming oxidised. Wine in porous vessels, like barrels, slowly evaporates during maturation creating ullage inside the barrel. They must be regularly topped up with wine to remove the ullage.

We explore Barrel Topping in the 1 minute Wine Bite – “The Angels are Stealing our Wine: Topping Barrels”

Large vessels, like tanks, potentially have 1,000’s of liters or ullage. Winemakers use inert gases, including carbon dioxide, nitrogen and argon, that don’t interact with wine to protect the wine from oxygen. Variable capacity tanks with lids that can be lowered onto the wine and then sealed are common in wineries.

Historically, some cultures would use olive oil to form a layer on top of the wine to protect it from contact with oxygen.

Ullage levels in bottles wine are given names or measurements depending on bottle type. The diagram below, courtesy of LeDomduVin, shows those names & measures.