New trends on yeast autolysis and wine ageing on lees: a bibliographic review

In enology, lees are mainly used in the traditional practice of « sur lies » wine ageing, which consists of carrying on the contact between wine and lees (yeasts and vegetal residues) during ageing. Lees come either from first or second fermentation, and could be used for white or red wines elaboration. Such an enological practice remains yet empirical. In the present paper, the state of art was investigated in order to collect and analyze most of the scientific works realized on wine lees. It includes also technological points relevant from such a practice. A clear definition of wine lees from legal and technological points of view was given in the first part of the present paper. A second part described the mechanisms of autolysis and focused more precisely on each class of identified autolysis products. Many scientific works had indeed revealed the yeast autolysis phenomenon occuring during such a way of wine ageing. All these works remained mainly based on identification of yeast macromolecules released in the wine during the autolysis phenomenon. However, the experimental methodologies followed by the different authors are variable, and most of the obtained results were difficult to extrapolate to actual wine ageing on lees. Only few works dealt with the physicochemical properties of such lees during autolysis, specially towards oxygen, polyphenols and other wine compounds. A compilation of recent data obtained on these peculiar topics was then given. In a third and last part, the effect of ageing wine on lees was approached from a technical point of view