Oxygen consumption by wine lees: impact on lees integrity during wine ageing

During wine ageing on lees, periodic stirring of the lees and repetitive additions of small amounts of oxygen to the wine is generally performed traditionally and empirically. Although this technological step is thought to have a significant impact on the organoleptic composition of the final product, little is known about the interaction between oxygen and lees during such a process. During simulation of wine ageing on lees, we now show that some membrane lipids of yeast lees, in contact with dissolved oxygen, even at very low concentration, undergo a mild oxidation. These oxidation reactions lead to the production of lipid peroxides and then to the production of unknown end-products. They are primarily due to the production of reactive oxygen species (ROS), and totally explain the capacity of yeast lees to consume oxygen during wine ageing. The lipid oxidations within the plasma membrane are responsible for strong modifications of plasma membrane order. Some of the final products of oxidation reactions may play a favourable role in the organoleptic equilibrium of wines aged on lees.