head space, that space in a container holding a liquid that is not taken up by that liquid. In wine containers it is often called the ullage, or ullage space. In large, modern wineries, the head space of stainless-steel tanks is often deliberately filled by an inert gas as a preservative measure. Similarly, many modern bottling lines use inert gas to exclude oxygen from the head space.
© Jancis Robinson and Oxford University Press 1994, 1999, 2006, 2015